[MENTION=13820]bpatters[/MENTION] You're right, there are more kinds of flies than just fruit flies and that's probably why it didn't work. There are plenty of common species that it could have been, like gnats, drain flies, house flies, bluebottle/blow fly, fermentation fly...there are others, but these are the only ones I can think of that you could find indoors.
What do they look like, [MENTION=35836]nmhofherr[/MENTION] ? About how big are they? Are they brown, or more colorful, like an iredescent blue or green? Because depending on what kind they are that might explain how to get rid of them. But when in doubt, use fly paper. They all fly around so that's bound to get most of them, at least.