The conventional explanation of the run-away greenhouse effect,
which produced the conditions we see on Venus today, is that
the evaporation of water vapor caused the temperature to rise so
high that the atmosphere became unbound.

I have seen a journal article that says the temperature would reach
'several thousand degrees' until the surface could 'radiate in the
visible'.
This is absurd and impossible. In fact I am sure the temperature on
Venus has never been significantly hotter than today.

First of all, even if the surface did reach such temperatures, it
could
not 'radiate in the visible' to space, as the H2O atmosphere would
be completely opaque at all wavelengths. Even if there were no clouds,
it would be nearly opaque in the visible due to Rayleigh scattering.

Second, where does the heat come from? No sunlight will reach the
surface, so the only source of surface heating is internal heat. On
Earth today internal heating of the surface is roughly 1/5,000 of
solar
heating; on Venus it must be much closer. But regardless of the heat
source, convection limits the surface temperature to a value that
increases only logarithmically with pressure, and is proportional to
the adiabatic lapse rate. In an atmosphere saturated with H2O at
high temperatures ( 100 C), the lapse rate is very small; therefore,
even though the atmosphere is think, the temperature will surely
remain below the critical point of water as long as the atmosphere
is mostly water.

When, however, the planet has lost most of its water to
photo-dissociation, the base of the cloud layer will lift off the
ground and the surface temperature rise because of the increase
in the lapse rate (the amount of sunlight getting through is
irrelevant
as long as the atmosphere is in convective equilibrium). This
results in the conditions observed on Venus. What happens when
the last of the water is lost? The cloud layer then disappears, but
the surface temperature won't decrease unless the amount it can
now radiate to space exceeds solar input, which seems unlikely
unless the CO2 atmosphere is so thick as to be opaque in the
visible from Rayleigh scattering (several times Venus).

Andrew Usher