SOLVED! Recruited Katja from Boneyard library and she unlocked it for me.

So I killed the guards a while ago when scouting, and now gone back with the three paladins... but I seem to have missed out on picking up the code tape, and now all the dead bodies have vanished! Any suggestions how I could get inside?

Perhaps you picked it up without realizing it? I seem to recall the code was in a, what appears to be, regular holodisk which you have to use like all the others. If not, and it really is gone, then perhaps an inventory editor?

Thanks, I solved it since. I recruited Katja from the Boneyard library and she unlocked it for me.

Glad to hear :) Happy raiding!

Thanks!