How themes are purchased and licensed is controlled by Chrome Web Store, not me. The licences is tied to your
google account, so log in the account you purchased theme with. Go to
https://pay.google.com/payments/u/0/home?utm_source=googlepay&utm_medium=website&utm_campaign=sign-in#activity. You should see all purchased themes for an account you are currently logged in there. If you don't see them, then you probably purchased them with other account or maybe it's bug with Chrome Web Store. You should be able to install purchased themes for free. For example, I'm able to install the theme I purchased half year ago on my pc and laptop.
Sellers in Chrome Web Store can't really yank themes from you, they only can give you a refund, but in this case your money will be returned to you, so it's not really yanking.