My Sim used the Ghost Potion to cross the chasm at the Copper Quarry then over to the single dig site on the small island. I noticed he'd been there a while and the potion was running out of time. I gave him an order to cross the river as soon as he was done digging. I cycled back to him just as he finished, with only a few minutes of ghostliness left. He started drifting towards the river. I was hoping he would revert over the river. I wanted to see what would happen. He might have made it if he hadn't stopped to yawn after digging. The potion ran out just as he reached the edge of the island.
Has anybody else seen anything like that happen, when the ghost potion runs out at an inopportune time?
P.S. edit
He used Escape Dust to return to Base Camp.