@Janna that is infuriating and personally, I'd be demanding a full refund if not pursuing legal action for the loss of your data. That is something EVERYONE who works on computers knows, to respect other people's data, even if it's just pictures. Those pictures might mean a lot to a person. I'm sorry they failed you so badly.
Have you tried any of the undelete programs, some of it may be salvageable IF the data has not been overwritten yet. I don't want to give you false hope however, the chances are slim but you might get something back if they just did a simple wipe.
Files are not really gone until they are overwritten, formatting basically just frees up the space unless a person deliberately writes 0s in all sectors. A person must deliberately erase these by writing over them many times and government can sometimes even get them back after that. It's best to do this as soon as possible as files may take the original place of the files you want to recover.
http://www.officerecovery.com/freeundelete/ I cannot speak for this program but don't think it installed anything bad when I tested it on my PC. It asks for the drive to scan for. If any files are found they will likely have very strange filenames. I'm VERY sorry if this doesn't work and I gave you any false hope, but it is worth trying.
Regardless of if this works, you deserve a refund after a talk with the manager. They got lazy.
EDIT: If that one doesn't work, there is a paid program that will let you get 100MB back before the trial expires. It sounds like if you got just about anything it'd help
You could be selective and perhaps get the most important stuff.
Wondershare.
Edit2: the first program (
freeundelete) I linked let me recover some fallout 4 screenshots I had deleted previously. I suggest you do this ASAP so that nothing overwrites the data. I HAD emptied my recycle bin. It will tell you the quality of the file. If it's good, chances are it will be intact. I wish you the best, let me know how it goes.
