Don't worry, it'll find some materials to work with.
Most of the phylactery's surroundings are constantly changing, but not all. This is why you don't mess around with phylacteries, kids. Leave it where you find it and tell a grownup.
(Everything that follows should be read in the voice of Wayne June, voice actor from the acclaimed video game Darkest Dungeon.)
To the phylactery and its recently discorporated inhabitant, the world is now a blur of matter and spirit--no place for the delicate work of reconstructing a paranormal body. But at the center of the shifting chaos, there is a backpack, and orbiting the backpack is a circle of self-styled adventurers who, in their delusion, believe that what they carry is dead.
Any one of these fools will serve, to start. The Thing asserts its will on one with a weak mind and sturdy flesh. The work begins cautiously, to avoid alerting the others--the priest of Sarenrae could do real damage to the Thing in its current state. Through its new host, the Thing gains faculties: awareness, memory, speech. It learns that they plan to sell the bauble to a local merchant. It riles the party's greed: this monger's purse will hardly suffice for their trouble. No, they must travel on, to the great city of Absalom, where the gods of the markets are strong and all things sell for their full value.
The host suspects nothing, but the hedge-witch among them is a bloodhound for any whiff of occult power, and confronts him one night outside the camp. She is not carrying her book of magic, or her wand. The Thing has grown comfortable in its new flesh, and the host's muscles are trained to execute this task.
She was possessed, the Thing whispers to the host, in his own voice. The phylactery was in her pack, and it took her mind. She would have killed you. Best you take it and keep it safe. The Thing takes a moment to appreciate the symmetry of the lie, then permits the host to scream.