My feeling about those "color catchers" is not that there is something magic about them but that they just pick up some of the dye that bled into the washing machine water like any other fabric would (which is why washcloths work just as well).
I always prewash my fabrics once and then if I am suspicious, I test a washed sample while the larger piece still sits in the washing machine (blues, dark greens, blacks mostly--for some reason reds don't seem as prone to bleeding). I put hot water and a tiny bit of detergent into the bathroom sink and with the drain closed, wash and rinse the sample several times so I can see if the water remains clear or not in the sink. If it still bleeds, I run it through the washing machine again (and again, if necessary). Some fabrics just never seem to clear up.
So sorry this happened to you--but it's true that oftentimes our own mistakes are much more obvious to us than to others!
Dana