Don’t get your hopes two high
Actually, it’s not unheard of for debts to disappear and then reappear. It probably has to do with collection agency re-selling your debt.
Most collection agencies re-sell uncollected accounts to other collection agencies. It happens all the time. Some companies update your account balance to show $0, other simply delete it. The new collection agency that bought your debt probably hadn’t updated the credit bureaus yet, but may do so in the future.
As long as the 7-1/2 year reporting period hasn’t passed, the debts can show up on your credit report later.
BTW, did they disappear from all three credit reports or only just one? If they still appear on even one credit report than you won’t benefit from it. Most creditors pull your credit reports from all 3 major credit bureaus.
It also has nothing to do with your liability to pay the debts. The 7-1/2 reporting period has nothing to do with the Statute of Limitations (SOL) which is the legal time frame to file a lawsuit against you.