Except any sufficiently advance race will realize long distance communications is a must for technological growth. EM is the only practical way of doing this that we know of. My SETI search does not require an active search by another civilization. Just the fact of using EM will be enough thru unintentional radiation of EM into space like our civilization is doing now.
We might not recognize a signal even if we were looking right at it. For example, an analog AM or FM carrier stands out way above the noise, but digital broadcasts make better use of bandwidth and are thus more noiselike. A highly exploited bandwidth would be indistinguishable from noise.
There may be a window of only a hundred years or so in which a civilization is advanced enough to put out a detectable signal but not enough to make full use of bandwidth.
How high into the EM spectrum are you searching? What waveforms are you looking for? Last I knew anything techincal about SETI, 20+ years ago, they were looking for extremely narrow band, long persistance signals. Not like anything we use, which are either short duration, or wide bandwidth, or both of course. We are also moving way up in the spectrum. It's not completely out the question to use lasers for space to space communications, in fact I thinks we've done that already, at least on an experimental basis.