Unfortunately recovering individual photos from a TM iPhoto library was dropped from iPhoto's capabilities with iPhoto 9 as I recall.
The possible sceanario you gave is the only way to do it. Restore a library that has those photos, open it with iPhoto and export them to a folder on the Desktop, import the photos into your current working library and then delete the resotred library.
If there are not too many and you know the file names of them there may be a way to recover them without restoring the entire library. The method can be time consuming – up to 5 minutes per search. If they are all in the same event it makes it possible3 to get them all with one search. Post back with answers to these questions if you're interensted and I'll lay out the how to.
There is a possible way to recover those photos:
Restore a library that you're pretty sure will have those photos. Make sure you select "Keep Both" when asked:
Then use the paid version of iPhoto Library Manager to merge the two libraries into a new, third library. With iPLM's preferences set to not import duplicates you should get just one copy of very different photo in both libraries. You may also recover other photos that you have deleted but those can be redelected.