Jonathan - Why did you unhook the bottle before it was empty?
Disposable tanks have characteristically had problems with their
seals, which is why most folks leave them connected to an
"appliance" when not in active use (and why the manufacturers state
that they are not for re-use/refilling). That way, the
torch/regulator controls will keep the gas contained. Otherwise, you
would need to consider disposable tanks as “single use”, which they
are not. For many years I used, and taught, with a Bernzomatic
plumbers torch. For melting I used Bernzomatic’s MAPP gas turbo
torch. Now I have a wide array of torches, but I still teach with
Bernzomatic if that is what my student(s) have access to.