Translation:I seem to have lost my number. Can I have yours?
No kidding. It's called "learning from context", and Duo would be 200% better if the sentences had context. But it's 4 years later, and they have not taken your suggestion at all. It's really a shame, because Duo could be a top-notch language program, instead of just being somewhat between mediocre and good.
No, it is just dumb. I suspect the question was meant to be "I have lost my telephone. May I use yours?" . They added the word "number" by mistake, which turns it into a nonsense. (And if it is supposed to be a pick up line, they could have accessed the number when using their phone anyway.)