I've not had a good experience with them either. I was contributed a bug fix to the std lib which would've been a decent feather in my cap. Not even a thanks; some maintainer copied, pasted, made a few changes, merged "his" fix. 2014 iirc; extinguished my interest.
It's more likely to be downvoting an unsubstantiated allegation of plagiarism which, in the circumstances, could easily be argued with public evidence.
You seem more uptight about it than I am. I didn't see it as anything so formal as "plagiarism", I just thought it was rude and ungrateful. If digging up work from 2014 is easy, you must be more organised than I am.
If you made a attempt to upstream the work (what most people would assume from “contributed”), it will be in Gerrit [1], which allows it to be found using the “owner:<email>” search.
