Poached eggs dissolve while cooking?
The likely contributing factors are (and probably more than one, and perhaps all apply):


Older, weaker red wine vinegar, which didn't sufficiently acidulate the water to denature the egg white proteins quickly, thus removing their ability to dissolve
Older eggs, with weaker, looser whites that spread more easily in the poaching liquid, and thus dissolve more easily due to greater surface area
Lower heat of the poaching liquid which would also slow the cooking of the white, allowing it more time to potentially dissolve before the proteins are denatured from heat, and thus can no longer do so