Clone Of For Richer or for Porter - Low Eff Brew Session

Missed my pre-boil volume by a __GALLON__! How did that happen? Batch-sparged. 2.5 gallons mash volume, added .5 gallons of 180*F sparge water for 10 minutes. 2x vorlauf at 2.5qts each, then dropped my first runnings. Drained the mash tun, and added 2.5 gallons of 175*F - sparge water, and sat for 10 minutes. 2x vorlauf at 2qts each, then dropped in my sparge into the kettle. Measured volume and I was at 3.6 - gallons!? I calculated my absorption at .1gal/lb, so how did I end up a gallon short? Oh well. Quickly did a 2nd sparge with 100*F - water, about 1.5 gallons for about 10 minutes. 1x vorlauf at 2qts and wort was pretty clear (dark, but no grains). Drained into kettle, and barely got a gallon out of it. I had to tip my mash tun to get a little bit more out to get near 4.45 - gallons in the kettle. Oh well, live and learn! Beer smells good, so I hope it turns out good!