I have switched from a toothpick to a high-powered magnet. It is shaped like a large Tums disk. I cut the tip off the finger of a rubber household glove to act as a "gasket". Works like a charm. Just remove the lock, wipe the barrel clean, and place the magnet/gasket over the touch hole vent. I also pack a patch or piece of paper towel in the lock inlet as a drip catcher just in case.
I learned this magnet tip from Ron Hess, and he has my thanks.
On a round breeched barrel I still use a toothpick. I leave the lock in place, and the frizzen is closed on the toothpick to keep it in place. I also trap a cleaning patch to be first line of defense against a drip or leak.
Here is my tip: I have some microfiber car cleaning cloths you get at Target or Walmart. I keep one in my range box, and before cleaning I tie it around the stock tightly behind the breech. If anything were to leak, it would be caught before running down the stock.
Just some ideas that work for me.
OP, I am sorry you had this bad experience. God Bless, Marc