There was this article that quoted his last sighting as Saturday evening. I don't know if this has ever been restated, corrected or confirmed.
Searchers narrow time frame of Merritt cowboy's disappearance
"At this point, RCMP say they have determined Tyner would've likely left on Sunday, however it's still not known how he got into the backcountry."
"We know of his whereabouts on Saturday night, so that gives us an extra day," Dunsmore explains. "We are still looking at how he may have gone up here, because we're still thinking that maybe he was driven up. So we don't know who would have driven him up, or if there's anybody out there that maybe brought him up with a truck and trailer, and we're looking for that person if that did happen."