Quick question about slumping bottles...

Hello all,

Last night hubby and I fired several cobalt blue glass
bottles in the kiln for cheese trays. They turned out
absolutely fabulous, but. One of them apparently rolled
during the process.

Question. I think I read somewhere
that one can place a few grains of sand on each side
of the bottle to prevent rolling. This is assuming nothing
happens to the kiln such as bumping, it is level, etc.
Does this sound logical? Will the sand dissipate into
the glass of the bottle?

Many thanks for any tips.

KM