I did a year end close on a company and worked in the next year for several days without a problem. Opened up the company today and it had reverted back to where it was preclose. How can that even happen?
I've never seen that happen. Many people make a copy of their company before closing the year. If you do that, the more likely explanation is that you opened the wrong company. That's very easy to do since Sage 50 usually remembers the last company you opened. It's also possible that a backup was restored.