Sometimes building out a 'wizard' for these types of scenarios are worthwhile and help the user navigate — you've a choice on which info to provide but you must

Sometimes building out a 'wizard' for these types of scenarios are worthwhile and help the user navigate — you've a choice on which info to provide but you must provide at least one (as you described). But on shorter forms (e.g. "Add a gift message" on an online order), I think they can be overkill, both extra dev effort but also extra friction for the user. ETA: just when you say — " I think in this case we're looking at a required input with an optional lookup workflow -- if you have that extra piece of information, you can take a shortcut." That's another distinction too — I think this is true of the business process as a whole, but possibly not all within this form. For some businesses, it could make sense for this to be just one more data point that's sent along in the message rather than trying to build out a completely automated form submission (e.g. if the ticket was going to be picked up manually anyway)