THC, or any cannabanoid for that matter, does not evaporate. Water does. Crumbly dry bud=very little to no water present.

One time I forgot about a nug in a drawer. Was there for maybe close to 3 months. It was powdery and dry as a bone. I put some flame to it and it was hard to smoke but it got me blazed big time. Potency was just fine



About that sealing jar lids. I have had that happen and believe its just the moisture that builds up inside the jar during the cure. Kinda makes the lid stick because of that rubbery material around the rim. Just my take on it.