Zelle transfers into an institutionally insured checking/savings account at a major financial institution are pretty safe and people will get their money back. Zelle transfers from non-BoA accounts will have the records at the other banks to prove the transfers existed and they can be recovered that way. If BoA really lost the records and don't have backups and people lost transfers from BoA to BoA accounts and neither BoA account has a record of the transaction, it will just be a hassle for customers probably having to fill out some forms and wait a while.