I started a Belgium style ale, about 1.064 og. After 2 days I go check on it in the fermentation fridge and see that the lid of the bucket has blown open, blown the fridge door open, and krausen was everywhere. I don't know how long it was like this. I obviously closed it up again and closed the fridge. Is the beer still fine to bottle? How do I prevent this in the future?
I would presume the beer is still good to bottle - but leave it (at least) for a full 14 days before attempting to prime/bottle/keg. I have had the plastic lid blow off the fermentation bucket on previous occasions. I put it back on and continued with the brew. Once the beer was a little more sour than I might have liked but it got drunk anyway... The rest was fine.
2 days after pitching the yeast, the beer should be fermenting vigorously and so the action of the yeast and hops should keep it relatively free of undesirable micro-organisms. In such situations I remember Belgian Lambic ales. They are fermented in open air with the lid of the fermentation vessel (barrel) removed. They are a popular style in Belgium.
Fermenting Belgian ale in a fridge is a novel idea. I am not certain if cooling adds much to the final product but I always approve of experimentation. To prevent the top blowing/flipping again, the gas must be allowed to escape from the fermentation vessel. So either the bubble trap (or vent) got jammed with krausen or there was no bubble trap and the lid of the vessel had snapped shut. Both situations would allow the pressure to build sufficiently to pop the top. Bubble traps often get "plugged" if the air space above the wort is small. The foam/krausen rises and gets forced into the bubble trap often blocking it (sometimes it blows free and the top stays on). In such a case use a bigger fermentation vessel or brew less beer at a time. If no bubble trap is used then consider fitting one. If the "old school" way of leaving the lid unsealed is used as a venting method then make sure the lid does not (somehow) snap back into place - effectively closing any vent for the CO2 produced during fermentation. Sometimes a bubble trap on top is too tall for a specific place (like a fridge) so, if all else fails, drill a few holes in the lid and cover with a plastic sheet/cap using some tape (on one side) to keep it in place. This is an easy way to let gas out and prevent most stuff dropping in. Good luck!