We're having an internal debate on which I would appreciate some community input.

If a consumer calls the bank to confirm whether an expected direct deposit (or other authomatic credit transfer) was made to their account and learns that the credit was not received or posted, does this situation trigger the bank's obligations under Reg E's error resolution requirements? Is non-receipt of a credit the same as the "omission of an electronic fund transfer from a period statement"?

The wording of the commentary to 1005.11 implies that it is, if the consumer asserts an error at the time of the call.

How are others handling this scenario?

A literal reading of the phrase "omission of an [EFT] from a periodic statement" could mean that an error claim can't be made until the periodic statement is prepared (could be a month or more away) and the entry is missing. A practical interpretation, I think, is that the customer is about 99% of the way there once the bank representative knows that the customer is looking for a particular EFT credit and it has not yet been credited. All that is missing, I think, is for the bank representative to offer to investigate and the consumer to give the go-ahead to do so. Now you have the requisite parts of the error claim.

It won't benefit the bank much to tell the customer to wait to see if the credit shows up on the monthly/quarterly statement.

On the other hand, the bank is not really in a position to do much investigating. It doesn't have to reach out to the Originator of the ACH entry (it may do so on its own); all it really needs to do is to look through its incoming ACH credit files. If there's no credit there for the customer, then the bank's response is that the bank did not receive the entry, and that the customer should contact the Originator.

Ok; if, in the course of checking the ACH file, the bank finds a transaction for the consumer with an incorrect destination account number. Should that discovery lead to a Reg E prescribed error resolution process?

I can only assume that your review of the ACH file was precipitated by the customer's call to inquire about the credit. You've begun the investigative process. You've found what appears to be the reason the customer didn't get the funds credited to his account. You've more than begun the process; it's darned near completed.

That's what I thought. We have the same investigative challenges whether the error is alleged at the time of the call or later, after the statement is generated. We only have so much information on a transaction that didn't happen, and that's what some of team was concerned about.
Thanks for your comments and happy holidays!