the HP manual refer s to it (Jumper #29) because the location does exist acording to your statement
there is a world of diffrence between "does not exist" and the location exists but the 2 pin header is not soldered in
since ER15 does exist but lacks the 2 pin header, you can take it to a local repair shop and have it installed for a small fee
once done you can try a recovery
i do not own a z220 so i cann't confirm that jumper 29 is the one needed for recovery, but where i live a local repair shop will charge about 40/60 US dollars to remove the board, install the jumper and replace the board. they also will not give any warranty on the work other than it will power up and off just as it did when brought in