Don’t know if it rained. And current exhaust is pretty soot-free.
Oh, I just assummed that it had a plate of some kind on it. If there was no plate on it, it certainly could have been a torch that momentarily got too close.
For a nice clean appearence, I removed every front plate holder I’ve ever had. The only front plate on anything I own is just bolted to the front bumper of my 79 and says ‘‘Princess’’.
Last November I bought a used vehicle that was from a two-plate (front and rear) state. As I live in a one plate state, I was chagrined to find that the front plate holder was attached with huge rivets. Since the empty holder looks really bad, I’m in the midst of having a front plate made of the logo of my favorite band-LIttle Feat.
FEAT! FEAT! FEAT! I still remember where I was when I heard Lowell George died. 
I do.
Hypothesis it is.