strange clutch bleeding behavior. No solution needed.

[Dave Glubrecht]

Vehicle is T44 chassis turbo Quattro apx 1989, never looked as it didn't
matter.
Helping a friend fix his clutch.
Clutch pushrod had broken due to misadjustment.
Needed to pull the clutch master to fix.
Fixed linkage and reinstalled with propper adjustment.
Car sat overnight with fluid in the resivoir (doubt this matters)
went to bleed the clutch today and was a pain, but got it. with help of a
pressure bleeder using apx 10 psi
Had a good petal, BS'd for 15 min and when he went to back it out it just
stuck to the floor.
Blead it again same procedure, mostly just using the pressure bleeder and
opening the plug on the slave.  occasionally pushing the petal to move the
air to the outlet and then reopening the bleeder plug.
He got in to leave and went to the floor AGAIN.
I decided to try something different and reverse bleed it (pressure fluid in
the slave) as I have had success with this before.
We needed a piece of hose, so we went to the store.  When we got back apx 15
min later the clutch petal felt good!
This time I went to drive it out and it worked fine.
He left.
  WHAT HAPPENED???????
I have blead many clutches and can't explain this.
Dave G