When you install the bionic arm, it "removes" the hand - and the hand will show up as deleted if you show hidden items in the Character Editor. (The Character Editor might be an additional mod I can't remember)

So to get the foot or hand back, go into the Character Editor (after installing bionic arm/arms) , and click the "Show Hidden" option on the Health Tab, and remove the deleted fingers/toes + hand/feet entries.

Then you can install the bionic hand and bionic foot onto your bionic leg/arm and wear gloves & boots again.

EDIT: Actually, it's a little easier. In the character editor, you only need to Delete the Removed Hands and Delete the Removed Feet and then you can install the bionic hands and/or feet onto the bionic legs / arms.