[Closed] A piece of PVC tubing in my Genesis carbon frame?

Bought a second hand frame (Genesis Zero carbon) a couple of months ago, but only just got round to building it up.

Was about to fit the bottom bracket and looking inside the frame, there was a piece of blue 6mm diameter flexible plastic tubing running from the downtube across the bb junction and into one of the chainstays.

Its not related to the internal cable routing, cos I have those thin sheaths for that. And cabling doesn't run in the chainstay either.

I've pulled it out and its maybe a foot long. Just plain 6mm flexible tube.

Would it have been part of the moulding process and the previous owner never noticed?

Or any other ideas?