Collision at first

[Bagman62]

A Crash, Train Wreck or other no call as from you description the contact was unavoidable. Had F3 moved into foul territory and BR adjusted their base path I MAY have called OBS on the other hand had the BR established a base path in fair territory I MAY have called INT with dead ball, BR out and returned the runner to 2B.
But as you said HTBT.