Got this girl’s number despite never talking to them before. Don’t know how to open.

My roommate had some friends over and I knew a few of them so I was comfortable talking with them. One of the girls I hadn’t seen before was very shy and reserved so we never really spoke to each other. Later that night my roommate came to me and said “By the way, \*\*\*\* left this for you. they were to shy to give it to you.” It was like a printed business card with her name, number, and a Linkedin QR code. Since I’m pretty certain of the fact it wasn’t a networking tactic by them, I’m not really sure how to respond. The only times I’ve gotten someone’s number is either through asking them (never ends well) or being given their number after already knowing more about them. With this person I literally have nothing to open up the convo with.