So, I think I may have figured out what was happening with the OQO losing sight of the integrated Sprint Mobile Broadband modem.
What was happening was this: After some amount of usage, usually from 30-90 minutes, the computer would drop the Sprint connection and tell me “Device Not Found” or “Please Insert Device.”
I have a new theory: What if the power management settings are to blame? I often go to “max battery” mode, with the hope of squeezing every last drop from my extended battery, while I'm traveling (and I travel extensively). It dawns on me that the OQO has the ability to power down the device to conserve battery usage. It further dawned on me, that at least anecdotally, it seemed like every time I had the issue, I was on “max battery” mode. Starting last week, I've been careful to use “portable/laptop” mode instead, and I haven't experienced the issue since.
I'm keeping my fingers crossed!