First, you need to look at the terms of entry--if the terms specified that entries would not have to be returned, then they don't have to return them; that is a perfectly legal term of entry.If you have a right to have them back, on the other hand, and the chair of the contest won't return them, you could bring a legal action--that is, file a lawsuit--seeking either the return of the cars or their value (if they were destroyed  or damaged). However, there is no mechanism to get them back other than by a lawsuit, and filing a lawsuit on a party in another state can be difficult and costly--among other things, depending on all the circumstances, you might not be able to file it in your local courts. (Check the rules about jurisdiction and venue and relate them  to the specific facts of your case.) And unless it was a very valuabel model, then an attorney would almost certainly be cost-prohibitive. This may be a case where you do not have any effective remedy.