I have an '03 X5 and found the BMW hood emblem gone with no signs of vandalism and half the sticky mustardy colored waxy glue still there in the chrome holder. Is it common to fall out during driving on older models?

I've never heard of it "falling out" it's common for the clear coat to chip away, even the blue sometimes, but I've never heard of it just "falling out"

Professionals can do it without making any mark of vandalism left behind.
trust me, I have had mine stolen few times, and I have caught the person once.

is the whole emblem missing with just 2 holes showing or is it just chrome showing and you cna make out where the color use to be

mine went missing also...and there was just the round chrome showing...but it does not necessarily mean vandalism...mine was gone after i went to a car wash...BMW replaced it for free under warranty....it looked ghetto tho lol