I requested a custom item a few days ago and if I am not mistaken later in the same day it appeared in my inventory.

The first problem I noticed was that it had no location in the inventory and was not at my current location, the second problem was that the CPs were not deducted from my total and when I logged on today the item disappeared from my inventory.

Unfortunately I did not memorize its entity ID number.

If no CPs were taken, then there is no problem. Just reapply for it. Otherwise, contact the Art Team Leader as they will most likely know what went on as they deal with all that sort of stuff.

Alright, thanks. By the way do you know if I need to be on the surface of a planet for the item to spawn (like CP bonus ships if I am not mistaken) or it'll spawn wherever you are?

You can spawn custom item wherever you want. After approving by Art Team, CP should be deducted from your account and item should appear at the same place.

The item appears as soon as it is requested, but it still needs to be approved. We've had people try to sell illegal, unapproved stuff before. If it disappeared, I'm guessing it was declined.

I'm assuming the same as Hal. Since the item appears as soon as it's requested, but without a location, the fact that it subsequently disappeared makes me believe it was declined. Before you reapply make sure that whatever you're requesting follows the rules set out for custom items.

I double checked and it seems to me that the only thing that they could have issue with is the 400x300 image (probably not of good enough quality for them).

Another thing that came into my mind was if requesting a custom weapon is a no-no or not.

Also, shouldn't I get a notification whether or not the item is accepted or not and in the latter case why it wasn't?

If you requested a weapon as a Custom Item, then that's a definite no-no.

I should have expected as much. Any way I can withdraw the request?

No, you'll just have to wait for it to be rejected.