Lost Photo Library

If you do not have a working backup, only data recovery software can help. But recovery software is expensive, and the chances is slim that it can recover files, it the deletion has been a long time ago and your mac has been low on storage. Recovery software is trying to find data on disk blocks, where the deleted files have been. It can recover them, if no new data have been written to these blocks.

You could try a program like Disk Drill, that has a free trial version. You can see, what can be recovered, but will have to pay, before you can save the recovered files:

  https://www.cleverfiles.com/iphone-data-recovery.html

Give this a try: Hold down the Option key and go to the TM menu in the menubar and select "Browse Other Backup Discs…". Then select the same disc and see if you can go back farther in time.

Have you checked the Pictures folder in your Home folder if the library "Photos Library.photoslibrary" is still there? You have also checked the Trash folder in the Dock?