Since I have NO IDEA of what ruleset you're playing under.....I'll apply your question to what I do.....Men's ASA slo-pitch.
In MY case.....I'm LIKELY to DISREGARD the contact.....unless I have OBS. Where, exactly, did you say the F5 was standing (duh?)?
I'll protect the R2.
Like I said......I'm likely NOT going to acknowledge I even SAW the contact at 3B......and if pressed.....would also likely issue a warning to F5 to STAY OUT OF THE WAY OF THE RUNNERS.
I have no idea of the EXACT "book" protocol. I'm telling you what "I" would do.
Let me have it guys!