But here's a clue. In the subsequent descent with static pressure increasing and the pitots still blocked?, even though the airplane was actually stalled (complete with stick-shaker) the indicated airspeed would be increasing alarmingly - courtesy of increasing static pressure. That's my guess - and it's anyways a physical fact, Been there and done that trick with frozen trapped water in the static lines (i.e. the opposite effect of trapped dynamic pitot pressure). There's also a report on the Irish Accident Board's site about a 747 on a test flight with uncapped static lines due maint error. It's an elucidating gaelic tale that shows just how confusing the pitot-static scenario can be. See below for how much a 1000feet of altitude change is worth in terms of additional "displayed knots". Ask any instrument technician. That's what I did. He'll demo it for you on his test-bench.
Well, as an example of how confusing it is, I happen to have my Jeppesen basic IFR book here, and it seems to say the opposite:
The second situation occurs when both the ram air inlet and drain hole become clogged, trapping the air pressure in the line. In level flight, the airspeed indicator typically remains at its present indication, but no longer indicates changes in airpseed. If the static port remains open, the indicator will react as an altimeter, showing an increase in airspeed when climbing, and a decrease in airspeed when descending. This is the opposite the normal way an airspeed indicator behaves, and can result in inappropriate control inputs because you will observe runaway airspeed as you climb, and extremely low airspeeds in a descent. This type of failure can be very hazardous because it is not at all obvious when it occurs
As an aside, what's wong with a good, old-fashioned idea of having a small red or yellow ribbon on a small stick which is bolted just outside cockpit window? Shine your flashlight out at it and it will give you a very fast indication of what direction the air is going past the airplane.