is there a way to check a gun to make sure it was not stolen before you buy from an individual you do not know without being a ffl dealer?

Contact your local police department. They will run it for you.

thank you. i thought they would.

Be prepared to answer a lot of questions if the gun comes back as stolen. Also, ASK BEFORE YOU BUY. If you ask afterward, and it comes back stolen, you will have to forfeit the gun and will almost certainly lose your money.
I worked in a gunshop for several years. We would do this occasionly and we had one come back as stolen. The police asked a lot of questions to where the gun was, how did we get the serial number if we didn't have the gun in our possesion, did we get the seller's ID numbers, address, etc., could we give a description of vehicle he was driving...well you get the point.
I have been friends with many police officers here in my town and have asked the same question. They all said the same thing...if it comes back as stolen, you will be spending some "quality" time with a detective.
I personally think this sucks. There should be a website that you can go to and find out for yourself....just don't see that ever happening.
Just be careful, I don't want you to have any bad experience with the police or the possibility of losing money.

One caveat is that with so many firearms in existence, and coming from multiple manufacturers and countries, serial numbers overlap.

The LEO databases for stolen firearms often don't make the distinction about what type of firearm it is (rifle, pistol, carbine, etc), although to be fair sometimes that information IS listed.
Therefore, a "hit" for a stolen firearm may turn out to be for another type of weapon, say a pistol instead of the rifle you're looking at.

It's a very, very imperfect system.

I've often thought the best system of all would be a database that all members of the NRA could participate in. You could list a stolen firearms description and serial number, and you could check against that database when you purchase one.
I think that would be a real boon to the majority of us who enjoy firearms.

Garrett