The post does not explicitly suggest the writer was claiming ownership of the reply which is sort of common knowledge at the time. It's a news headline, and we regularly see different media houses use very similar headlines for their publications. If the op had written more which was copied without including a source, it would then be in the realm of plagiarism, imo.
But still, it would consider as plagiarism or copy paste. For such a post, OP should mention there that "
I have read on Telegram (source name) or on news". Also at least OP should use Quotation mark (") on the post to avoid plagiarism. Add source link on the post also help avoid plagiarism. If this isn't plagiarism then many users will do the same. But, really this wouldn't consider as heavy plagiarism. Most likely temp ban for such a case would appropriate IMO.