Yes. You need to look not at the in's and out's, but for buttons.
Buttons labeled 1/2, 3/4, STEREO OUT, etc. Or something similar.
You may not be able to buss individual channels out the stereo buss without affecting others, but it's worth a look.
A buss is a signal path that individual signals from channels are grouped into. Say channels 1,2,3, go to buss one for a drum mix on track one of a tape machine. Channels 4,5 go to buss two for a backing vocal on track three, and so on. This is opposed to individual outs like you are using your inserts and auxes for. Each of your inserts or auxes is a direct out to a tape channel or "virtual tape channel" in a computer in which one signal from one channel goes to one tape track. There is no grouping of individual channels together to send them out of one output.
As a stereo buss functions it usually groups all channels to a Left or Right channel assignment depending upon the pan knob. If you have individual assignments for each channel you may be able to route your last two remaining channels that have no where to go, out the stereo buss. That is, if you can keep the other channels off of the stereo buss while you are doing it.
That's why I said earlier it depends upon the configuration of your mixer. Many manufacturers have varied routing options, even within thier own product lines.