You don't say where you are initiating this from - property sheet or vb editor. It's been my experience that sometimes if I choose the object and event while in the vb editor, then write code for it, the connection does not seem to be made to the form object - even if [Event Procedure] is showing on the property sheet after doing so. The 'connection' I refer to means the event would not run until I clicked the builder button on the property sheet event line. This took me to the code I had written - and the event would run thereafter. So, I'm saying it's best to create all events associated with db objects by using the property sheet to begin with. Not sure if this is a bug that creeps in after a lot of design changes and no compact/repair ever having been done or what.
However, it does not explain why your written code is missing. For that, I can't think of what it could be besides you not saving your changes? Two similar procedures, one not 'connected'?
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.