Just a guess, but if you run diskutil list from Terminal, the Recovery HD partition is reported as type "Apple_Boot", whereas the visible partitions are reported as type "Apple_HFS". Perhaps that is the reason the Recovery HD partition doesn't normally show up in Disk Utility. The small partition of type "EFI" normally doesn't show up either:
I've since added it back manually,
How did you do this? Does it boot and function normally?
Yeah I was just reading about the Apple_Boot type, still haven't found a way to do this to any of my own partitions, unfortunately.
Manually, I just created the smallest partition I could and then used Disk Utility Debug to "Show All Partitions" - on my original Lion installed HDD, then I just restored "Recovery HD" to the new small partition on the new drive, and changed fstab to not automount it.
Now the annoying bit is that it shows up in Disk Utility (which isn't so bad) and I haven't looked up how to keep it from mounting in Windows, but other than that it works fine. I'd just really like to put it in the same hidden condition as it was when I originally installed Lion.
I just found this outside thread:
Missing Recovery Partition After Cloning hard drive
From post #7 there:
You can set it to Apple_Boot using gpt and this is indeed what hides it from GUI apps like disk utility. Apple_Boot is just a hidden version of Apple_HFS; the recovery partition is just an ordinary journaled HFS+ volume that can be manually mounted with diskutil mount disk0s3 (or whatever slice the recovery partition happens to be).
To change a GUID partition type to Apple_Boot one needs to know the UUID -- which for reference is 426F6F74-0000-11AA-AA11-00306543ECAC -- and remove the partition using gpt then re-add it with the desired type. This won't destroy the data of course, but one needs to make a note of the start and size values of the partition (as shown by gpt show) before the remove and then use them when re-adding. See the manual page for gpt.
From post #12 there:
Through some accidental research (don't ask…), I found that Lion's version of Disk Utility will also restore the Recovery HD partition when using DU's Restore to image a Lion Partition. I verified this several times. If there is no Recovery HD, it will recreate an existing one from the source HD to the destination, and will be positioned immediately following the Lion partition.
If no Recovery HD exists in the source, but does in the destination, it will leave the destination alone. For instance, if you have an image of a Lion partition, but for some reason, no Recovery partition, you can do a clean install of Lion on the destination - creating a Recovery partition - then restore your Lion image to the destination (replacing the clean install). It will leave the recovery partition alone at the destination.
If no Recovery HD exists in either source or destination, I don't believe DU will create one - this is one scenario I didn't test.