You slept on the water, where there usually isn't anything mosquitoes are interested in.
In one of our worst mosquito years, when I took this picture while walking a short grass farm road near midday:

we were barely bothered while sitting in the water teal hunting:

But, lordy, did they eat us alive crossing the low grass cow pasture between there and the trucks. Must have been a bazillion and seven of the little bastards that were tired of cow and anxious for something different.