I had a similar problem - I made a huge mistake yesterday by going into System Preferences, left-clicking on the printer I wanted to connect to, and clicking on the "Reset Printing System" which led to a box that said "Are you sure you want to reset all of your existing printer queues and all pending print jobs?" and then I clicked OK. I thought it would cancel any open print jobs (and there were none open) and reset the printer that I was trying to connect to. What the prompt SHOULD have said is "DO YOU REALLY WANT TO DELETE ALL OF YOUR PRINTERS???" Because that is exactly what happened. I searched for a very long time on these discussion boards and on the rest of the Internet for a way to get back all of my installed printers. Why not just reinstall them? Because I had way too many network printers, local printers, etc. and all with their own customized settings that I couldn't remember. But I finally found the answer, and I hope you don't mind me posting it as an answer to your question, but when I found your post I was upset that no one responded because I also really needed to know what to do. But I did fix it, everything is back to normal, so this is for all those folks out there that are in the same situation we were in.
Here's what I did:
Step 1: Open Finder, go to Macintosh HD > Users > (YourName) > Library > Printers. That folder should be empty since you deleted those files when you reset the printers. Leave that folder open. Open another Finder window and go to your Time Machine backup. For me, the path was TimeMachine > Backups.backupdb > (2011-05-19-034706 - use your latest backup date, this is just the date of my last backup) > Macintosh HD > Users > (YourName) > Library > Printers. That folder should have some files that have your printer name.app (i.e. hp officejet 5500 series.app). Copy all of those files , and paste them into the Printers folder on the first Finder window we opened above. Now, close both those Finder windows.
Step 2: This is a bit tricky, as we now need the Mac to show us some hidden files, copy those files, and then hide those files again when we are done. Do exactly as follows to avoid any problems:
Open the Application Terminal (in the Utilities subfolder)
At the prompt, type these two commands (hit enter after each command)
defaults write com.apple.finder AppleShowAllFiles TRUE
Now, hit Command-N to open a new Finder window (or just open it from your dock). Click on your Macintosh HD under Devices, then you will see a bunch of folders that are normally hidden. You want to go to the etc folder by double-clicking it. Then, expand the cups folder and you will see the ppd folder. On your Hard Drive, it will be empty since you deleted those files when you reset your printers. So here's the path in case I confused you: Macintosh HD > etc > cups > ppd. Now, open another Finder window and go to the same path on your Time Machine backup. For me, it was TimeMachine > Backups.backupdb > 2011-05-19-034706 > Macintosh HD > etc > cups > ppd. You will see that folder should have some files that have your printer name.ppd (i.e. hp officejet 5500 series.ppd). Copy all of those files , and paste them into the empty ppd folder on the Finder window on your hard drive. You will be asked if your sure and to type your password, so just go ahead. It will be okay.
Step 3: We are not done yet. There are some files in the cups folder that we also need to copy from the Time Machine backup into your hard drive. So keeping both those Finder windows open, go up one level to the cups folder (on your hard drive, Macintosh HD > etc > cups ; on your Time Machine backup, TimeMachine > Backups.backupdb > 2011-05-19-034706 > Macintosh HD > etc > cups. Copy the following files from your Time Machine backup to the hard drive:
Now, there was a file on my hard drive in the cups folder that was not in my time machine backup called cupsd.conf.O that I didn't know what to do with, but I figured it couldn't be good. So I copied it into a temporary folder (just in case) and then deleted it from the cups folder on my hard drive.
Step 4: You are almost done. Go to System Preferences and click on Print & Fax, and you should now see all your printers back in the list. Congratulations, your printers have been restored! But we still need to hide all those pesty hidden files and folders in Finder, so close all open windows and go back to the Terminal application and type the following commands (hit enter after each command):
defaults write com.apple.finder AppleShowAllFiles FALSE
Then close your Terminal application and open a new Finder window and it will be back to normal with no hidden files or folders showing.
You now have your printers back to where they were before you hit the same "Reset Printers" button that I did (in error) and took me 2 hours of research to figure out how to undue the damage, or had some printers deleted in error when installing an unsupported printer.
If for any reason this doesn't work for you, all I can say is that it worked for me and I wanted to share the fruits of my labor with others who are in a similar predicament as I was. I am by no means an expert in this area, so although I don't see any reason why it wouldn't work, you just never know how one persons computer differs from another, so I apologize if it doesn't work out for you. But I really think it will, so good luck and happy printing!