Hey TheVertiego,
Thanks for the report! Chromie has not been on sale since last year. It should not have been possible to buy her for 350 Gems at this time. Please check your transaction history on the Blizzard Account Management website. It can take some time for newer transactions to appear on the transaction site; your gems may have been or may be in the process of being refunded. If you continue to have issues, please put in a ticket with our Support team.
Thank you,
~ Fizivix