So I had Arcade as a follower, trying to unlock his quest. (The game is on pause) and im browsing fallout wiki about Big MT. Then I come across how you can find two holotapes of Christine and Ulysses, so me being oober-excited about this I run to my console, un pause it and quickly send Arcade to the 38 and I transport myself to big MT. Blah blah found the tapes, came back to the Mojave, tried looking for Arcade everywhere, hes GONE. So, this is a bug right?

First of all, should probably be in the bug report section of the DLC forums, a mod may come across this and move it. However, with the patch before OWB, there are 2 terminals, one in the Gun Runner HQ and another in the Lucky 38. There are very distinctive from other terminals and shouldn't be hard to miss. I have not used them myself but I believe their purpose is for what you are describing. Good Luck.

Thanks I'll try that.

Please let us know if it works or not.

Do you have a saved game before starting Old World Blues, just in case it doesn't work?

He's most likely at the Old Morman Fort.

It worked, I went to the companion terminal, dismissed him then found him at the Mormon fort. Thanks guys.