Miscellaneous payment received into Undeposited Funds

We received a payment for a truckload of paper sent to a recycler, payment received by check.  We did not invoice for it as we don't know the amount that will be received, so when the check comes in there is no "customer" to apply a payment to.  It is a miscellaneous check deposit into Undeposited Funds.  What is a good process to use for handling miscellaneous receipts by check that aren't from a customer but that we want to be recorded to Undeposited Cash?  I'm looking through the Help data for miscellaneous receipts and it doesn't seem Intuit QB has addressed this, or perhaps I just don't know the right words to search for ...???  Anyone have a similar situation that you've handled successfully?