To continue
Once again, this AU Harry is much more perceptive of Snape than I would credit his canon self with. In addition to his awareness that Snape doesn't act without cause, he mulls over some other great details that ring satisfying true to any Snape fan: "It never boded well for him when Snape started to lose his temper. His biting tone was one thing, but when it felt like a real bite, that was quite another," and "Snape never gave up until there was no hope at all, and even then sometimes he could be pushed just a mite further." <3 Also, the chipped mug is one of the strongest images that stay with me after reading. Snape's cranky possessiveness and protectiveness of an old, cracked mug must be endearing to a Harry who could see himself in the place of that old mug.
I'm not at all sure you intended all the subtle insinuations and double entendres that leaped out at me nearly every other sentence (eg. "Snape hadn't acted like anything was out of the ordinary at the time, but Harry could never be sure if Snape felt the same things he did."), but just the existence of all those wonderful possibilities, regardless of intention, makes this piece a treasure. Treasure, hah. One analogy I'm pretty sure was deliberate is the jewel-encrusted scabbard = Harry one. Both go sailing off the cliff and both are snatched back by someone who cannot bear to lose it/him. The set-up for this runs throughout the fic from the first moment Snape declares, "Only to save your neck" (and from him, a confession of interest in keeping Harry alive is as good as a confession of love).
Which brings me to how cleverly the prompt is utilized (and how well this story suits its genres), since I'm supposed to consider those factors in judging. XD Wizard archaeologists! That's a concept that should really be explored more.
This comment is getting a little long even for my standards, so I think I'll cut it off awkwardly and thank you for a truly entertaining tale. :D What a story you've created!