I think they mean that they auto bought right before the plunge and are now frustrated because if they had procrastinated a few more days they would now be in a position to buy low with the same money.
That being said, trying to time the market tends to be a losing game for retail investors, as statistically the market is more likely to rise than fall, so earlier is better unless you have better information than the people paid full time to study the market have.
Molecules of dihydrogen monoxide, a chemical commonly found in rocket exhaust and which has been linked to the deaths of thousands in the last year alone, discovered to have made its way into local water supply.