Backroad Anthem lead singer Craig Strickland, 29, and friend Chase Morland, 22, vanished after tweeting about a trip into "Winter Storm Goliath" near Tulsa.
"In case we don't come back, Craig Strickland and I are going right through Winter Storm Goliath to kill ducks in Oklahoma," Morland tweeted.
Strickland, who recently married to 2014 Miss USA contestant Miss Arkansas Helen Wisner, retweeted the message.
The duo was last spotted two hours after they set out.
His band is asking their fans to pray for Strickland's safe return - posting on their Facebook page, "The power of prayer is huge. #prayersforCraig"
"We can't even stand to think about it. We are devastated. Only God and time can put us back together," a family statement said.
Searchers found the men's capsized boat in a lake in Kay County.
Strickland was believed to be on a boat with Morland as the area was besieged by record rainfall and flooding.
Searchers found Morland's body in the lake.