I don't know how many rows your table has, but no database engine I'm aware of keeps secret hidden audit log tables to mimic user tables so this type of question could be answered. Imagine how much that would slow performance! Sometimes it would be worth the cost and other times it wouldn't - they let us decide for ourselves by giving us the opportunity to keep a insertedDT column if we choose to.
hmmm...
Yeah I was just wondering if there is any way to determine it from the log that the MySQL Engine maintains.. Even if it does it won't keep the log for years I guess...
Sam gave me some money, and then Sally gave me some money. Now I have $50. How much did Sam give me?
Finding when a particular row was inserted into your database table if you don't record that is as impossible as answering the question above. RDBMS engines don't store data unless you ask them to. The amount of potential metadata that could be stored will always amount to a great deal more than the real data you actually store.
The way to get this information going forward would be to add a RowCreated date column and default it to GetDate().