Tabs gone, reverted to backup??

Please help!!!!!! I looked away from my phone and it had turned to a black screen with a small little loading wheel and when it turned back on it had deleted all of my opens tabs as well as the private ones and reverted back to old tabs open from over a year ago. I tried to re open the tabs by pressing the plus button to manually open each tab but they were gone from there too. Im so confsued and the tabs i had open were open for a reason and i needed them to help track important information i needed.. all of the tabs were gone and im so lost on what happened and why. Please help me understand how to get my tabs back and what even happened.