I don’t know if it was a grift, but it sure sounds like boundary testing to me. Like, if you’re willing to give up the last number of your SS number (because it’s “no big deal”), then what else are you willing to share? And eventually, that could indeed stack up to enough information that it could be compromising, or it could be totally benign, but it’s an odd enough question that it stands out. Why didn’t they ask about your phone number or your favorite number? Those feel more like getting to know you questions than your SS number. ETA: I meant to say, you were very wise to trust your instincts. I’m just mentioning the “boundary testing” for people who may be unfamiliar with the concept or who, unlike OP, may have been inclined to not listen to their gut out of politeness.