Two factors are at work
1 - When you freeze the water, you have to leave the top off the bottle, because water expands as it freezes and otherwise it would split.

What then results is a bottle of ice with a bit of ice sticking out of the top where it has expanded.

When the bottle is left out to thaw, it doesn't of course all melt at once. The outside melts first, including the outside of the bit of ice sticking out of the bottle neck. It has nowhere to go as the bottle's still full of ice, so it trickles down the outside of the bottle, forming a puddle on your table.

2 - Air contains water vapour. When you leave the bottle out to defrost, it will condense and freeze on the surface. Eventually it will melt and run down the side of the bottle, enhancing the puddle.

So in effect, you do end up with more water than you started with, because of the condensation.
( K2k6 has a proper job these days, Fri 4 Jul 2008, 10:33, Reply)