Small claims court or I'd suggest unfortunately take the loss as a lesson ( re not negotiating a price based on down-riggers not being available at pick up) ....and move on. For court you'd do best to have proof of the inclusion of the riggers with the boat sale ( promissory note/IOU receipt /e-mail). Otherwise the seller could just say that there must have been a misunderstanding as a verbal deal was reached that did not include the riggers (even if that was not fact as to what happened) . The seller however is looking rather bad right now as they appear to be ignoring several diff methods of contacting them ...... all while they apparently have been logging in to this forum. You could just link (or cut paste) the boat ad in another thread and title it "The Boat My Parents Bought" or just a photo of the boat and title "The Boat My Parent's Bought From Forum Member ____ ;-) lol .
But more seriously I am a little concerned that if this seller is in fact not providing the buyer with the goods promised but paid for, that they then could very easily do the same to other buyers on here if the site admin's policy is to not allow a member to be called out for a possible bad sale on the forum. Would it not be in the best interest of admin and the success of the site/ Buy&Sell forum to, at the very least, contact the member who is being accused and attempt to find out what happened? If for example the admin can not be satisfied that the member has behaved appropriately in the selling of an item, can they not just revoke their membership? As a member and buyer on this forum I can say if this isn't policy in these cases, I 'd think hard about using the site to buy anything. The one safety net I thought we had here is that it was harder for a member to rip off another ( less likely ) due to the membership sign up.