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It's possible that they were backed up because Time Machine creates backups automatically. However, you must know that you can't restore individual photos in iPhoto, so you have to restore the whole iPhoto library.
To restore the iPhoto library, read "Restoring data from Time Machine backups" > http://support.apple.com/kb/HT1427 You have to go to the folder where the iTunes library is
If your intention is to recover additional photos from those already in your iPhoto Library and intend using a "Restore" from Time Machine or another source, first keep a copy of the original "iPhoto Library" with a different name, to avoid over-writing.
You can hold the Opt key while opening iPhoto to see what libraries are present on the system and select one to see the contents.
If you want to merge the two libraries, there is a facility in "iPhoto Library Manager" to do so. It has other functions, to search for duplicates etc. I have not tried this and am not sure how successful it is at keeping album structures and photos with the same name but different contents.
Always keep external backup copies of originals during such operations.