did you have a sync code? if you’ve setup sync and you’ve the code stored somewhere or in another synced device just coping the Sync Chain Code into another brave browser(on another phone or computer) will restore the Grouped tabs unless you removed the groups manually in your device.
i had all my tabs last night. i have no idea what happened but i literally just opened my browser this morning and more than 10 tab groups (and probably over a 100+ tabs) are just gone. there’s nothing in recently closed tabs and the only history showing is my desktop history, nothing for my mobile browser.