Stabilizers create directional stability - they keep the pointy end pointed forward. To do that, they must be mounted behind the rotational pivot point that the aircraft rotates about, the center of gravity.
So when a airfoil or control surface is mounted forward, in front of the center of gravity, (canard), it cannot, by itself, be functionating as a stabilizer, (even though we may refer to it as a stabilizer). It is, in fact, only a horizontal or pitch control surface.
In this case, (a forward mounted canard), the canard is not creating directional stability, the rear-mounted main wing creates this directional stability (pitch stability) about the lateral axis. The canard itself actually detracts from directional stability. It is there to provide control about the lateral axis.
A vertical stabilizer is there to provide directional stability about the vertical axis (yaw or sideslip stability). You can't mount a vertical stabilizer forward because there is no other vertical airfoil at the back providing directional stability about the vertical axis. Or perhaps it might be more accurate to say you could, but only if there were a larger vertical stabilizer in the back. In which case it would be pointless to put another one in the front. that would be reducing stability and requiring the rear-mounted one to be bigger.
An example here to illustrate the point might be the AIM-7 sparrow missile. It does have it's horizontal and vertical control surfaces in the front. It has fixed wings at the aft end of the missile (which are the stabilizing airfoils), and movable control surfaces somewhat forward of the C.G. It maintains a constant* roll attitude and can maneuver in any direction (left/right/up/down), without rolling or changing its bank angle. It does this by deflecting the forward control surfaces as necessary to create lift in the desired direction. So, it effectively does have it's horizontal and vertical "stabilizer" (actually, control surfaces) forward of its fixed stabilizing airfoils.
*NOTE. although actually, in the F-4 at least, the AIM-7 was programmed to always initially roll and then maintain a roll attitude where its wings and control surfaces are oriented in an "X" configuration relative to the launch aircraft, not as a "+" the way you might imagine.