I'm afraid my response is too late to be of much use to the topic-starter, but maybe someone else will be visiting lovely Maastricht some day in the near future. So here goes. As it happens, one of my best vegan friends lived in Maastricht until recently. She came up with the following tips (for another forum).
Right by the trainstation Maastricht is the Cubico café. You can get a tasty pasta and salad. Only two things on the menu, but she says they're good.
There's Gadjah mas in the rechtstraat (near the trainstation, there's also an organic/healtfood store) has a vega menu, with tofu saté. http://www.gadjahmas.nl/
Ceramique has been mentioned before. Is said to be vegan friendly. http://www.eetcafeceramique.nl/
There's a vegan friendly Italian place in Heerlen. Has several vegan things on the menu.http://www.dapeco.nl/
Luik/Liege is relatively close by. It has a vegetarian burger restaurant.http://www.tastyworld.be/
Another person in the same thread suggested the Thai restaurant http://www.tabkeaw.com/
You can request tofu with every main course (as a replacement, I am guessing, it wasn't clear), and they even have a vegan alternative to oyster sauce. And it's reasonably priced.