Had a similar situation happen to me just today. I was googling to see if others had used FMI to locate lost (stolen?) iPads and stumbled across this post.
I left my iPad 2 3G 64gb (in a Booqpad case) sitting on my work vehicle this afternoon and I drove off - yes, absolutely stupid of me. Not surprisingly, at some point while driving around it fell off the car.
When I realized i lost it, I looked on FMI and saw that it was unable to get the location. I figured either a) it had passcode self-destructed after 10 failed attempts or b) someone intentionally turned it off (it was on when I lost it) or c) it was destroyed. I hoped that it wasn't a or b since I had my business card fixed inside the booqpad case.
About two hours later it popped up on FMI about 22 miles from my home. I sent several messages asking to call me and return my iPad. No response for an hour so I called the police. Good on them for understanding how FMI works, so they had a plainclothes patrol meet me at a strip mall near the residence. The police suggested flushing the guy out with a finders fee, so i sent that message; my phone rang about 10 minutes later. The guy now wanted to meet and return my iPad. He showed up at the local strip mall where we agreed to meet (he looked like a 19-year old hair band throwback) and the plainclothes police had a few words with him and some matching bracelets for him.
I opted not to press charges since it looked like the iPad had indeed been found by the side of the road. There were a couple of scuffs in the case and the corner of the iPad was a bit dinged up (still works fine though). The business card with my information was gone, however. The guy also claimed he didn't receive any of the messages until the last one with the finders fee - his logic was "finders keepers...unless you want to buy back your stuff from me". I didn't want my iPad to become state's evidence for the next two years, so the police gave him a good butt-chewing and sent him on his way.
When I got home I also noticed that the battery was topped off - it was at ~60% when I last saw it. Interesting...
What I learned:
1. Don't leave iPad on top of car and drive away
2. Find my iPhone works EXTREMELY well - enable it!
3. Make sure you disable slideshow from the passcode lock menu - in my case, the guy said he was going through my photos on slideshow to try to find out who I was
4. Have good police who understand how technology can help them solve crimes