its a possibility that the flight you saw will come back, you just have to be super vigilant. prices are all based on availability, so if someone else has provisionally booked those seats they will be gone from the inventory, but if they don't pay in a certain amount of time they will be released back into the system. usually. the airline could also withhold the inventory if they feel like it
best bet is to check super early in the morning and check lots of airlines, or use a comparison site. be prepared to pay as soon as you see something you want. you could also consider using a travel agent, as they will be able to hold seats for you for a day or two, so if your first choice doesn't come back, you still haven't lost the second best seats.
(but don't dick your travel agent around by asking them to do this for you and then booking online)
i am a travel agent