Since the portion used to pay off the loan appears to be a qualified loan offset distribution, you should have received two Forms 1099-R from the old 401(k), one for the amount rolled over to your new individual 401(k) (code G if done by direct rollover, otherwise code 1, 2 or 7 if paid to you) and the other for the offset distribution (code M, along with code 1 if you were under age 59½ or may code 7 of you were over age 59½).
With regard to a Form 1099-R that includes code M in box 7, you have until the due date of your 2021 tax return, including extensions, to come up with the money and roll it over to your new individual 401(k) or an IRA.
If the entire amount, including the offset distribution that satisfied the loan, was reported on a single Form 1099-R, contact the old plan to find out why the offset distribution was not reported separately with code M.
