He could have had the heist planned out before he left on the Arcadia trip and just went to carry it out in a rush. Have supplies stashed elsewhere to carry out his plan.
A tiny bit leery but I guess it works. There's just be a shorter gap for travel time and making sure that the shipment he's going for is actually happening/on time, in addition to getting his stuff.
@Flamelord
Do you need to have written out every part of his plan IC? You can't say he had this in mind all along? Maybe he took the Blue Relic in the first place for the sole purpose of having a tool for this heist.
Well I think the recent events just confirmed that he won't be using the Blue Relic on the heist, but it's a nice thought regardless :P