You have lost nothing really.. if the change was done 8 hours after the announcement.. you would have mined roughly the same quantity of coins with those 4 workers as you did now with only one.. so your income did not change much (or changed very little, close to nothing). In the meantime though.. some would have had some tens of thousands to pump/dump after the market opening.

Imagine 4 workers mining 60 coins each for 8 hours and 1 worker mining 200-210 coins for those 8 hours.. you loss is like 10-20 coins.. but it may as well be a profit for you. The numbers are exemplary.