#1 rule if you want to catch an ant: Always carry a small glass bottle or a plastic test tube around with you - you always find them when you're not actively looking for them.
But NEVER carry caught queens directly at your body - the excess heat from your skin can kill them quickly. Instead put them into your jacket pocket, bag or backpack.
Yes, it looks like Lasius niger (might also be Lasius flavus if it has a more yellowish lower side, they're pretty much the same except L. flavus gets yellow workers).
I'm sure you will have another chance to catch them, they usually fly 2-3 days in a row multiple times throughout the summer.
Lasius niger is btw a brilliant beginner species that thrives in pretty much every environment and is very forgiving even if you make mistakes in their keeping (same goes for Formica fusca). You just need to place the queen into a test tube setup with cotton and water and leave her alone for 3-4 weeks. She doesn't need any food and the water from the test tube is sufficient. When she has first workers place the test tube setup in a small plastic or glass container (don't forget to apply a barrier to the container top sides like baby powder or Fluon), put a straw through the cotton and offer a tiny drop of sugar water or honey and a fruit fly or a small spider.
I caught a Lasius niger queen about 20 days ago (they were everywhere) and she already has larvae =)