IE *p and *b

Hello,

I am new one to this group. My background - Lithuanian and Slavic
languages, at the moment I study Irish.

I have a questio re original *p and *b in IE. Somewhere around this
list people mentioned *b was rare (or non-existant) because it has
fallen with *w. This made me thinking - is it possible that *p was a
voiceless pair thereof, .i. [f] or bilabial [F] (phita sign of Greek
alphabet)? This would explain why *p was lost in Celtic - rather
enigmatic phenomenon. The problem remain how to interpret *bh - any
ideas on that?

Best regards,
Róman