Arnie, Wild Bill Hickok (correct spelling) died in 1876. Is that late enough for your friend's friend to have seen him? He may be recalling William Frederick "Buffalo Bill" Cody who died in 1917 and in whose Wild West Show, Hickok once rode. Buffalo Bill continued the Wild West show long after Hickok's death. it is common for people to confuse them

William Frederick "Buffalo Bill" Cody on wikipedia

and

Wild Bill Hickok on wikipedia

Apropos of nothing, a great great nephew of Hickok's by the name of Rex Hickok became a porn star and porn director under the name Rex Cabo. He went a bit nuts a few years ago and tossed himself out a window in Long Beach. I wrote an Obit for him. it was a sad story. He was clinically depressed, had gotten deeply involved in the Church of Satan but ticked off his fellow satanists with his weird stalker-type behavior. In the end, he holed hismelf up in some down and out hotel, called his shrink threatening to jump and hit the ground just as cops arrived.