I know this has previously been discussed at length, but I suspect my situation may be more specific. The other day, after some rain, I noticed condensation inside the driver's-side headlight assembly. I recall when replacing the eyelid bulbs knocking a small yellow thing off of the back of the headlight. I covered the hole with electrical tape. What was this and could this be the reason?

If so, what is it called so that I can order a replacement? Would prefer not to deal with the dealer and a TSB kit.