Hi Kevin, what does the stain look like? Does it appear darker than the rest of your stone or is it actually lighter and rough? The latter may actually be etching, which is resolved differently than a stain.
Lighter and rough. Its a very dark chocolatey marble to begin with.
Ok, what you are describing sounds like etching, and it is caused from contact with acids...so probably the vinegar...maybe toothpaste too! We use a special etch removal cream (sometimes a buffer if needed), to remove etching. You would probably have to purchase this type of cream at a granite supply store or online. We get ours from a stone restoration company out of California, Granite Shield, since we use their other products. If you do attempt to remove the etching yourself, (which i dont necessarily recommend), be careful not to scratch the stone by using something too abrasive... If you have a stone restoration company nearby, this should be a relatively inexpensive fix.