Patersbier is not, strictly speaking, a style. Meaning, it doesn't really have a framework of color, ingredients or flavors that can be used to group them together. It's a Monastic reference to being "Father's Bier" or beer brewed for the Monks, themselves. As such, they are widely different and extraordinarily rare. I've been told that they are usually pared down versions of Trappist commercial styles, but having had a couple, I'd say that is overly simplistic.
I'm prefacing my response this way because you might very well have a perfectly reasonable beer, depending on your ingredients and techniques.
Your hydrometer is calibrated for 60 F. warmer and the reading will be lower.
Candi sugar and other highly fermentable adjuncts increase alcohol, which lowers the hydrometer reading (the term is "apparent attenuation"). BeerSmith has an adjustment tool for that. I punched in your two numbers (1.045 and 1.000) and it shows a likely 1.004 final gravity when adjusted for alcohol.
The yeast you chose is a high gravity strain, capable of 12% abv and more. You may have given it merely a snack!
If you saw a healthy fermentation, then I will lean in that direction over a contamination. How long did it sit in the fermenter?
How does it taste? Is it fragrant, lightly fruity and spicy like black and green peppercorns? That is a typical clean Belgian profile. Does it taste like stale cinnamon, old cloves, over ripe bananas and a hint of Grandpa's closet? That is often a wild yeast contaminaton.