Killing a Vampire without Sunlight, Running Water or Wooden Stake

In the adventure module

a vampire is encountered guarding treasure in the same room where its coffin is. I am preparing to run this encounter, and the party is unlikely to have wooden stakes or access to running water or sunlight.

A vampire’s Misty Escape trait reads:

When it drops to 0 hit points outside its resting place, the vampire transforms into a cloud of mist (as in the Shapechanger trait) instead of falling unconscious, provided that it isn’t in sunlight or running water. If it can’t transform, it is destroyed.

While it has 0 hit points in mist form, it can’t revert to its vampire form, and it must reach its resting place within 2 hours or be destroyed. Once in its resting place, it reverts to its vampire form. It is then paralyzed until it regains at least 1 hit point. After spending 1 hour in its resting place with 0 hit points, it regains 1 hit point.

So if and when the party drops the vampire to 0 HP, the vampire will transform into a cloud of mist, fly across the room to its coffin, and revert to its vampire form, where it will lie paralyzed. Note that its Regeneration trait will not work while it has 0 HP.

At this point, can the party just kill the vampire by hitting it with one or more attacks while it has 0 HP? Or if not, what am I missing?

I know that the

in the room will complicate this, but not make it impossible.