While driving the oil filter fell off, all the oil pumped out, the engine locked up?

Hello, sorry to hear the bad news, there is an oil pressure switch but that would not prevent the engine from locking up in your situation. I think the garage that did the oil change is absolutely responsible for something like that. That is a case of someone rushing through an oil change and not taking the time to check if everything was ready for the engine to be started. It would be the same if I forgot to put oil in the engine and started it. I've seen that happen because the mechanic was trying to look good and fast. Shops have insurance for things like that. Although now it has been a year, I don't know how that would work. But that's a big deal. Even a used engine is very expensive.
As for trying to recover the engine, if it won't turn over by hand, (putting a socket and bar on the crankshaft bolt) most likely the bearings for the crank and camshafts are burned up. The oil pump would pump that oil out so fast, it's a sad situation when a shop won't take responsibility for their mistake. With the spark plugs out the engine should turn over very easily by hand. I'll post some pictures of what happens with no oil pressure if I can find some. But I'm very sorry to hear about this.
The engine life would be greatly shortened if you did manage to get it started. I think you'll have to do some research on what action can be taken at this point, considering the time that has gone by.


https://www.2carpros.com/articles/high-or-low-engine-oil-pressure

Thanks for your reply, I also think they should have replaced the motor cause the oil filters just don't fall off like that. So, someone told me to fill up cylinders with 2 cycle gas and let it sit for a few days and try and turn the motor by hand. So, i did and the motor turned a little going at it slowly. I'm letting it sit again and will go back and see if i can turn it a little more. will keep you posted.

Well, that's better than being completely locked up, I do hope you can get it moving. Oil additives may help too. It really depends on how fast the engine shut down during the pressure loss. If you get it to turn over, you'll need to do a few oil changes with filters to remove any particles that may be in the oil pan or oil passages.