Whether Luke was present or not I don’t how one would determine but if Matthias was NOT to be counted among the 12 then who would be? No other person is appointed by Christ to be so numbered and even Paul did not count himself among the 12.
“I rather think the number “12” is important and was reserved to Jesus alone”.
I agree and therefore must ask, ‘If not Matthias, then who did Christ choose to fill out the number 12?’ And if he did, when and how?
I have no idea. :-)