Needed documents with passport stuck in US customs - help?!

Hello,
My British husband and I currently live in the US. We had to send away my husband's passport to his UK bank as proof of identity in order to get stamped bank statements from a branch, which were requested by UKVI. The clearance officer who requested these (they're statements from a year ago) has given us a deadline of "by 5th August" (next Tuesday) to scan and email them to him. We paid for 2-day business day shipping from the UK, and they were sent on Tuesday. It's now Friday and we've just been told by FedEx that the parcel is stuck in customs at Memphis, where it's been since Wednesday or so. They don't know why and they can't tell us when to expect it. I suspect it has something to do with my husband's passport (his only form of ID), as I thought I'd seen someone else on this forum have similar troubles once they declared their passport.

Does anyone else have ideas for how we can get this sorted out? We are desperate to get these documents, and to get his ID back. I'm currently at a loss. Thanks and appreciation for any pointers.

 All you can do is wait.  As soon as Customs clears it, FedEx will send it.

All you can do is wait.  As soon as Customs clears it, FedEx will send it.

So there is literally nothing I can do at all? Since this happened, I had to cancel the final trip (before the move) to see one of my best friends over the next several days, in order to stay home and receive it, either today (very unlikely) or Monday in hopes I will receive it before the deadline. Someone has to be home to sign for it, so we've been housebound. We might not even get it in time now. I have never seen 2 day shipping delayed by several days due to customs. (Sorry, just venting, this has turned into a bit of a nightmare and is having a domino effect.)