In my opnion
Mandar purposely went missing as he had own plans and not keen to stay with Pallavi
But unfortunately met with an accident and saved by Raghav...
Later he was fine and gave dhamki to Dr. Janki about her life or something and went missing..
Lion and Mandar used to work together for drugs business hence Lion knowsMandar and Sharda both...RR ruined their business by sending Lion to Jail..
Lion cant attack directly after seeing what happened to Sunny, so he approched Mandar who was underground as memory loss and was running his business. Or Lion happened to meet Mandar luckly
None will challanged memory loss and Ambulance driver as Drug smuggler
When Mandar and Lion understood about Raghavs hospitalization and blood need so they created a plan....
Lion told him about Pallavi and Raghav...so he came back to take revange
Mandar was to get married with Pallvis friend but unfortunately she died and Mandar feels its coz of Pallavi so he wants to ruin Pallavi and Raghavs life now
Kya eisa ho sakta hai...