I was thinking more Kane/Undertaker (their final feud). Undertaker was still competing regularly after WM26 vs HBK, but got injured soon after. To write him off Kane said he found Undertaker in a "vegetative state" which is why Undertaker isn't around and Kane went on a mission to find his attacker. Eventually Undertaker returned at Summerslam and Kane attacked him and revealed to everyone he was the one who took out the Undertaker.
That's all I can think of for the reason for Reigns not being around. How is Reigns apparently communicating with Solo but at the same time not showing up on tv and suddenly just deciding to never return to WWE ever again and not even in contact with Heyman?