That happened to us here in France. We were riding with one of the french Elite Morgan Lavaux, the president of the trials association I am in and Thomas Francisco, BIU European champion sponsored by Koxx . We were riding on the Isle of Versailles in the town center of Nantes where there are awesome rocks and where you don't feel in town center because it is a protected area.
We left our bike down a section to check it out, butfrom the top of it, we could see three young people (15 16 years old) starting to take our bikes!
Morgan Lavaux is what you could call a truck driver (physically and psychologically, you don't want to make him angry). So he started running down the section, and so did we! We had to run after them for like 50 meters, and Morgan just jumped on the first one who had Thomas' bike (Koxx Black Sky). SO the dude fell off with Morgan shouting at him and ready to punch him in the face. I got Morgan's bike and My bike next because they started to slow down after what happened (Morgan was threatening them "If you keep going I'll make his jaws drop off!"
Morgan started to argue with the stupids cunst, and that day finished at hospital because we had to explain why one of the dude had his jaws broken and why the other had head-ache (his head hit the pavement!). Doctors and Police let us go (because they start knowing us with all the brake-noise)!!
Lucky us we still have our bikes but Thomas broke his on a comp exactly where Morgan jumped on the bike to make the dude fall off!