There is a similar clip like Demps mentioned on the clutch pipe but on an early car it's "closed end" - I don't think it can fall off.
There's a wire bundle to the relays etc in the vicinity of the booster that uses an open retainer. In this image the retainer and the bolt are near the end of the #9 arrow and under the circled 9. Similar retainers are used through out the under-hood area. I don't believe that retainer is closed. There's a few relays in the vicinity so look for a potential location on the dash panel/firewall.
'85 Wire bundle.png