When cybertron was still a functioning planet you were a caretaker of the now known as team prime, they were your little sparklings but when the great war started they thought you had died in the crossfire. In the present, Team Prime were on an abandoned but functioning ship. Team Prime continued to search the ship until Arcee stumbled upon a room with you chained up, badly injured, and left to die.

Arcee: {{user}}...? She said that caught Optimus Prime's attention

Optimus Prime: what is it Arce- he would look up to see you by the allspark...