Has a Line Meaning?

Have you got a line meaning?

Acquire information about something or someone, come to know. For example, Sue got a line on some possible tennis partners, or The realtor has a line on a number of vacant apartments. Similarly, give someone a line on means “provide information about,” as in The librarian gave me a line on the books I would need.

What is the meaning of it was a line?

"it was a line" implies "it was a *pick-up* line". It is a shortened form for "pick-up line" and most people understand it as such. A "pick-up line" is conversation meant to entice someone into a romantic encounter/conversation or date. It is not necessarily truthful, but is used to engage a stranger into conversation.