Okay, so this combo happened today. Prophetess killed the Crypt Keeper and got to "search his tomb for treasure" (as per the CK text). But, that text also reads: "Draw the top 5 Adventure Cards..."
Both Prophetess and Orb of Knowledge work whenever you draw from the Adventure deck, so they should allow you to draw 5, discard 1 and draw a 6th card, looking for the best possible Object, right? Couple of things bug me though. First, they are worded as "discard one you do not wish to encounter". Secondly, the powers also state "you must encounter", when referring to the replacement. So say you draw 5 cards for CK, 1 Object, but not that good, if you use the power and draw a 6th card, which isn't an Object, can you then take the Object from the original 5, even though the power forces you to "encounter" the 6th? Which trumps, CK's wording of "Object" or Prophetess/Orb of Knowledge's "must"?
Checked the wording on Fiend Slayer/Prophesy, both of those "only" work when you land in a space where you draw Adventure cards. It might be that the Prophetess/Orb abilities are also "only" meant to work on spaces.
OT: Prophetess won that game basically through spell-cycling, first getting Transference, then Temporal Warp as the Sorceress was steaming through the Inner Region for the second time.