Immediately lock and/or delete your card through your viva.com App or Account Interface. Locking and/or deleting your viva.com card will make it inoperative in your Google Pay App.
If you find your device after you have locked your card, you can simply unlock your card from your viva.com App or User interface and use Google Pay.
If you have deleted your card, you can either create a free new digital card from your viva.com App/Account Interface or order a new physical debit card and add it to Google Pay as before.