I did get 'absorbed' too, but i do not think it is related to shield. Perhaps you were in a party when that happened, because I think I was.
I also think that a vanguard visibly gets a shield around him when it procs, so I do think something is seriously wrong.
Well if it never procs, it cannot be effectual in PVP. That coupled with low DPS makes you a sitting duck, I would think.
Did you ever see the shield proc Seb?