I went to see caesar and lost rex for a long while even after I came back to the mainland, he eventually came back to me now boone is gone ,what to do ?

did you tell boone to wait and then forget to order him to follow you?

I just started having this happen as well,though with Veronica.

She will just stop for no reason and stand there and if you don't notice when it happens it is a long search to find them.

A reload worked at first but now she's just chillaxing in the middle of nowhere and won't budge.

I checked the companion wheel and she is on follow.

This has irked me to no end.

I am very irked.

I am having the exact same problem, after going to see cesar. She just stands around. Now I got her to return to the Lucky 38, and she is still doing the same thing after I add her as a companion. WTF?