Even tho' the airlock went empty, it probably kept any external air out -- that's the key, you won't want any floaters to enter ontio your carefully prepared culture. It had been filled with water, and the CO2 generated the bubbles, hopefully displacing any regular air in the chamber. The chamber was filled w/ yeast burps, heavier than air, anyway.. Even with the water gone, the available opening is very small, and the chance of external yeasts, bacteria, etc. getting in is probably very small. I think you're safe.
Put some more H2O in the top chamber and monitor it for a while... it's probably aged well. Please email us samples.
I wish I had your patience.