I accidently deleted files from a folder that is shared with me.
I can't find these files in the Trash. Is there a way to recover them?
If the files were synced with your computer, you can recover them if you have used a backup software (like Acronis, TimeMachine, DejaDup) and kept the backups for the period in question.
If the files were online-only, you can't recover them (http://support.google.com/drive/bin/answer.py?hl=en&answer=2405957).
Here's a blog article dealing with the same issue of recovering deleted Google Drive files: http://blog.backupify.com/2012/09/26/how-to-recover-lost-documents-and-data-in-google-drive/. Especially read the paragraph that starts with the title: Where Google Drive’s Safety Net Ends
(The company - no affiliation - offers 3rd party backup for Google Drive documents. You might want to try that for the future.)