I have a loan recorded on our LAR this year that was sold to an investor. The bank is now buying the loan back. Should I have 2 LAR entries, one for each transaction? or do I update the current LAR to show no purchaser?

You need to show 2 LAR entries:

5. Purchased loans. i. A financial institution is required to collect data regarding covered loans it purchases. For purposes of § 1003.4(a), a purchase includes a repurchase of a covered loan, regardless of whether the institution chose to repurchase the covered loan or was required to repurchase the covered loan because of a contractual obligation and regardless of whether the repurchase occurs within the same calendar year that the covered loan was originated or in a different calendar year. For example, assume that Financial Institution A originates or purchases a covered loan and then sells it to Financial Institution B, who later requires Financial Institution A to repurchase the covered loan pursuant to the relevant contractual obligations. Financial Institution B reports the purchase from Financial Institution A, assuming it is a financial institution as defined under § 1003.2(g). Financial Institution A reports the repurchase from Financial Institution B as a purchase.