I thought my arborvitae had little pine cones twirling around
Sounds like your arborvitae is infested with bagworms. This native pest can be very destructive especially to evergreens. If you want to save the tree, you need to start spraying as soon as you can. Spray with Bacillus thuringiensis (Bt), a biological control agent that you can find where pesticides are sold. This works well on young bagworms, has low toxicity, and does not affect humans or other animals. If the bagworms are larger than an inch, you can spray with Spinosad. Please refer to our website for more information about bagworms and what you can do. https://extension.umd.edu/hgic/topics/bagworms-trees-and-shrubs
Evergreens do not recover quickly or sometimes not at all from bagworm damage.
You should, however, spray to control the infestation. Bagworms can spread to neighboring evergreens in your area.