Shortly after being cloned, Bender leaves Delta Eridani for the Gamma Leporis system. He is the only one of Bob's clones that never connects to the BobNet via SCUT. His disappearance remains an unexplained mystery until Heaven's River, whose original working title was The Search for Bender.
The following contains spoilers!
For the younger generation of Bobs, he became a kind of legend, similar to that of the Lost Dutchman. Bender was presumed dead until Bob went looking for him and discovered that Bender had changed course after seeing an unusual infrared signature from Eta Leporis. The signature was caused by a topopolis megastructure called Heaven's River.
Bender's Heaven vessel was destroyed by the Heaven's River "Administrator", who extracted the intact replicant matrix. Bender was taken to the topopolis for further interrogation. It was subsequently intercepted by a local rebel movement, who used Bender to preserve and increase their knowledge about technology. Bender remained there until Bob and several other early generation replicants came to rescue him.