You can sue. What employer jokes about 'firing' an employee? It's not the correct work ethic, so it's their fault. You deserve work cover. Hope it works out!

Sorry OP! This is why I loath pranks, it's just another lie. But i guess you learned your lesson, getting laid off doesn't mean that your project is totally useless, you could use it else where.

try not to recover the project

Nope nope nope, get another job the boss is a dickbag.

Trash folder!

sorry OP. your boss is a jerk.

In my country that kind of prank would be grounds for a Constructive Dismissal case and compensation. At the very least I would find another job quick smart.

You should retaliate and prank him back. Restore your project if possible, put it on an external harddrive and say to your boss, that you deleted it because you got angry for being fired/pranked. Let the sucker roast in guilt, which is my desired outcome, for a few days and then magically find your project. In my opinion, you should scold your boss for even joking about such a thing because it's pretty serious business getting fired and having to find a new job.

That's a really stupid prank. I hope you still have it in your trash or that you have a back-up somewhere..

Normally I wouldn't advocate this, but if your boss has a supervisor at work, I would report him for extreme un-businesslike conduct. It may also help to cover your rear when it comes to why that project isn't done. I know that it wasn't mentioned, but it would be particularly bad if the project were for an outside company. FYL OP, your boss is a Class A Jackass.