Hello Constantine. It is slightly possible you will be able to recover the pictures, but this is already a bad situation.
The best option to recover the files would be to use the following software --
Depending on how you formatted the flash drive, it is possible to recover the pictures, but it may not be possible. The software above is a top rated recovery software, made to gather lost files on a USB, and the software is free.
Please let me know if you need any further assistance! If I have been helpful, please rate me!
If you have trouble running the software please let me know and I will be happy to assist you Constantine.
Please let me know if this has helped you! I use this to take care of my children and we only receive compensation if you respond back that it has been helpful. If it has not, let me know and I'll be happy to spend more time with you!