In GTA 4, does driving a particular vehicle make it appear more often?

Usually online, when playing with my friends, we have spent a little over an hour searching every corner of the map looking for a particular car/motorcycle with absolutely no luck. Yet, after much insistence, we find that precise vehicle and soon after, we have no trouble finding another one right away.
I remember looking for a Sanchez for over forty minutes without even seeing them in the street. Then, when I found one and got on it, I remember seeing three within a minute.
This is consistent enough for my friends and I to rely upon it when searching for vehicles "We only have to find one, then, we'll all have our own". I don't know if this happens to everyone or if it is just a glitch or a coincidence. Maybe there is a bug in the coding or some strange pattern. Anyways, it has been bugging me for some time now and I wanted to know whatever mechanism is behind this phenomenon.

You will definitely see more copies of your car once you start driving it, but the game will also load a set of other cars to be more realistic.

There is a also a slight trend for the game to load certain cars based on what you happen to be driving at the time, which you can then make use of to get the car you want (e.g. driving the Sultan RS causes the Sentinel to spawn more frequently).

Finally, some vehicles will always be loaded. These include service vehicles, dealerships cars and certain helicopters.