What I really want to know is, what you did after? Once you found out that rumor was false? Did you just say opps, and excused yourself or did you try make amends?
If I haven't confirmed something, I usually try to make that clear by stating "it is just a rumor at this point" or similar wording. I sometimes emphasise it by suggesting possible alternate scenarios that could have lead to the same rumor.
I figure that pretty much absolves me if the person I told spreads it as a truth.