Everyone knows that you now have 3 minutes to search for your ball, and if it isn’t found within that time it is “lost”. Bit what happens if you are looking for 2 balls (perhaps the original and a provisional or for two different players) in the same area? Surely you have 3 minutes to look for the first ball and another 3 minutes to look for the second one?
Sorry but the answer is “No”. If the expected position of the ball is close enough that you will actually be searching for both of them simultaneously then you only have one 3 minute search period. You would get two separate search periods if the search areas are separated – perhaps on different sides of the fairway – but otherwise both balls would become lost if not found by the end of search period.
Your 3 minute search period begins when you (or your caddy) begin the search. However you must not unduly delay getting to the search area and starting that search. A similar interpretation of “undue delay” would be used to that for when you are due to play your next stroke. For example it would not be OK to stop to admire the wildlife for more than a few moments, but it would be OK to stop and search for another player’s ball for a full 3 minutes while on the way to yours.