US Immigration from Wales

I had my interview on 13th Jan and what's frustrating is, when I filled my N400 73 years ago (slight exaggeration, I actually filed in my past life) I didn't owe any taxes, but since then I have been paying taxes via an installment plan.

They actually require you to present evidence of this as part of your citizenship, which I had no knowledge of. So I passed all the tests, just needed to give them another piece of paper showing my tax payments. The officer said that he would action the request for more information via a special form, (who's name/number I forget) and I can expect it in the mail in ten days. So seventeen days later I call up USCIS who has no record of anything being sent.

What I'm looking for is someone with knowledge of what I can expect now. It feels like I'm stuck and they could easily just lose track of me in what is, for Seattle filers, an absolute ocean of immigration backlog.

Will be moving back to the UK for a while and not having too much luck finding cheap shipping via sea.

It's kind of tricky to search because results keep coming up for general shipping (like fedex) or domestic shipping or shipping for businesses. Everything except sea freight for personal affects.

Just need a small ish part of a shipping container.