If you receive a check for a 1099-R retirement distribution, then you have 60 days to deposit that money into another retirement account (indirect rollover) or put it back into the account it came out of. Otherwise the distribution will be taxable and, depending on your age, subject to a penalty.
If you received a check and simply never cashed it, then you need to contact the custodian of the retirement account and discuss the situation with them. To be candid, I'm unsure whether that would be considered a distribution or not, since the funds never actually came out of the account.
If this is what happened, it's possible they could issue a corrected 1099-R to reflect these highly unusual circumstances.
