Wow - there are no words for leaving the chain in the pan. Probably fell in and responsible party hoped and prayed that it wouldn't cause a problem. Being heavy, it just sat in the sump until you found it.
I've seen those wing-nut
oil pan plugs before and believed them to be an "emergency fix" until such time as the pan can be either repaired or replaced. I once changed
oil in a 50-something Chevy that had a hard rubber plug driven in the hole. When I got it out the threads were fine and I as able to use a new stock plug. Previous must have lost the plug and found something that would work.
Go figure... Glad you able to fix it Ken.
This website will not be worth anything until if becones SECURE!
Not Secure