Doesn't help but this is why we don't put out any corn herbicide until it's planted, just in case.  Not saying you're wrong, others do it too.  We've had times, including this year, where we wished we had waited on any UAN or corn herbicide till it came up.  As I mudded in the last of the corn this morning dad was spraying what I planted April 29 for the first time since burndown, and it has only had the N from the DAP.  As I was leaving the field he got on the radio and informed me that he was thinking we could have just killed the corn and got beans on it later.  I can only remember one year where we had to kill corn to plant beans due to a bad stand, but since we had no corn chems down it worked out.  The last 10 acres we had planned on planting will be going to beans when or if it ever dries.