Chrysler Repair: oil change problem: drain plug fell out, torque specification, small claims court

Question
I have a 1997 Plymouth Breeze, automatic 4 cyl. I had the oil changed at a local shop and less than 2 weeks later my car died while I was driving. Had to have it towed and the shop I had it towed to said the oil plug was completely missing.  Oil had leaked out and ruined engine--I had been on the road that day.  I went back to the shop that changed the oil and complained.  They are telling me that the only way the plug could be missing is if something broke off a bolt/screw.  They said there is some kind of flange that would keep it from just coming off even if they had left it loose.  I would like to know if this true or any advice/questions that I should be asking.

Answer
Hi Brenda,
I know of no other flange (or bolt or screw) that would prevent (or break off) such as to allow the drain plug to come out of its socket on the oil pan. The drain plug is supposed to be torqued into the plug socket to 20 foot-pounds. That is about the same torque as is applied to a spark plug (which never come out on their own) and is sufficient if actually applied to the drain plug as to prevent it from falling out on its own accord or by external damage. In the absence of any damage to the oil pan around the plug socket there is no basis for any other explanation other than the person who drained the oil failed to torque the plug to the proper torque specification.
I believe the shop that diagnosed the missing plug is your necessary witness to what they found to be the situation when they examined the engine. They could also verify whether the threads on the socket were intact and capable of supporting a plug in the hole at that torque level. The oil changer could have stripped the threads if the shop finds that it won't stay in due to that sort of damage. If everything is 'ok' at the socket then you have the proof to seek restitution.  
I would get a lawyer or go to small claims court if you can get sufficient restitution that way and file a claim against the oil changer. Tell them you are doing one or the other action and invite them to pay for the engine to be rebuilt or replaced. They doubtless have insurance to cover such a claim.  If they demur, then move against them legally.
Roland
PS Please let me know how this is resolved. Hang tough!