Couldn't attend booked appointment

If you are local to the Netherlands Embassy and you have your appointment confirmation...

Arrive at the Embassy (or wherever your interview was to take place) when it opens in the morning, try to be the first in the queue. Show your confirmation to the security person and explain what happened in a brief way. Tell them that you would like to be squeezed in for any cancellations or 'no-shows' for today.

The security person will explain what to do next, but more likely will ask the consular staff what to do about you (that's why having the confirm is important). The consular staff will...

1. tell you to wait there until they have a slot OR
2. book you for another day OR
3. explain how to rebook online or at the VFS if there is one.

So the worst case has you knowing how to rebook, and the best case has you sitting your interview that day.

Probably some advice should go here about looking sharp, business like, congenial, and having all your paperwork organised and in order. Bring an interesting book because you might be waiting for a while in a 'no electronics' zone.

This a 'best practices' type of answer (i.e., I made it up out of the blue for this occasion), I do not know what the procedure is at the Netherlands Embassy. In fact I don't even know what country you are in. It makes sense that if you appear reasonable and earnest, that they would try to accommodate you as far as their procedures and prevailing circumstances allow.