Lyzelle, have you tried locating the starter and hitting it?
I know it sounds weird, but my Jeep did the EXACT same thing. Lights on, but nothing was working, not even getting a click from the ignition.
I automatically check the starter and battery before I check anything else, and the battery was less than a year old, so I started (haha) with the starter.
Found it on the Jeep, found a hammer, hit the b*stard and it started working again. I haven't had an issue out of it since, though I know sometimes with starters going bad you'll have to tap on them every time before starting the vehicle. It's worth a try anyway, won't take you ten minutes if you know what a starter looks like and where it is on your car. Pop the hood, tap (bang maybe) on the starter with a small hammer or a crescent wrench or anything really solid enough to make a good impact and then run jump in and try to start it.
Other than that, if you think that they've messed with the car, check your spark plugs, distributor cap, and fuses if you can. Pulling a fuse or a relay can cause the car to not start, so if they've gone and done something funny to it, those are the first places to look for something amiss. I can't remember what you drive, but at least a few of those would be accessible from the topside of the engine, and without a relay, or distributor the car won't start, but the lights will come on.
I know a guy drove a really old Cutlass and at the time at his work, cars like that were getting stolen left and right. So he'd take the distributor cap off and disconnect the wires and then no matter what the thieves tried the car wasn't going anywhere. Takes a smarter thief to check that stuff and they didn't exactly have time to play mechanic in the parking lot.