I reuse sand all the time, but I rinse it clean first, and then dry it out to store it. In my experience, sand taken from a system and stored wet in a compacted state gets simply gross. Add in the fact that it's donor sand from an old system, and to me it's worth a few bucks for new sand, versus hoping I get the old junk rinsed clear.
Also, it is true that anoxic conditions occur in standard bio-filtration, but they occur in a stablized, running reef with water flow, gas exchange, and two layers of cycle working in conjunction to export the byproducts. What's happening inside a bucket after a week is black nitrogenous decay.