I completely get why you did it and can definitely see it from your perspective however the reason it was probably taken down it since it wasn't an actual ad for a tangible item for sale it violated the terms of service of OfferUp. I think the better place in the future to post those kind of mornings would be here on the forum because that information is not only welcome here but it's greatly appreciated and hopefully someone will learn from your mistakes and not get taken advantage of.
Hello @Tony77 , Welcome to the forum!
I do appreciate your act of kindness and good intentions to warn the community about the scam. Right here, in the forum is the place to share, ask questions, and pass out a kudo or two.