@DDNeedHelp
Technically speaking, they normally have the mail forms or phone line to answer address related questions. Thing is, we were hit by the double whammy of under-budgeted IRS and non-essential personnel furlough. So now, they're neither solving the queue of several month-long snail-mail forms, nor are their phone lines working (except for the tax-refund lines, which are managed by script-stuck personnel and won't answer any question not related to a direct-debit or refund).
You can normally check the status of your address or how to change through the instructions on the IRS's website: https://www.irs.gov/faqs/irs-procedures/address-changes
On the note of a random bank crediting your check to someone else if they were to wrongly cash-it-in after having it wrongly delivered to them, don't worry. As far as the IRS is concerned, if a bank credited the check to someone they shouldn't have, that's their (bank's) issue. The IRS won't credit the funds to the bank unless you're the one cashing it out (personally, or someone else to an account opened to your name). This in turn means that as far as they're concerned, even if someone else were to do that, you never claimed the check.
If that were to happen, they'll certainly have a way to resolve the situation. One that they'll supposedly disclose in the upcoming weeks. As for now, I guess all we can do is wait.
I'm in a similar situation, as I also need to check what address they have on record for me, as all they're automated systems are telling me the address I'm writing is invalid/doesn't match their records when I only started filing taxes this year. Which shouldn't happen, 'cause once again, they should only have 1 address of mine on record. And I filed on January, so I don't think it's an issue of wait and see.
But hey, you know, government efficiency.
