On QXC and the like I would log 3 solos sent and stuff the CAA.
If they return it with a quibble tell them you de-briefed the student by mobile phone at each landaway and then verbally authorised him to continue.
Nowhere does it say that you must be physically present etc.
Its a jobsworth rule plucked out of thin air as it is.
Its easily and legally circumventable by all qualified instructors at a school 'giving away' all the their solo auths to the new instructor who then accumulates them at a prodigious rate.
If they are going to invent arbitrary rules then people will treat them arbitrarily.
WWW