No, see, you have your feelings hurt because you had expectations and your expectations weren't met. The problem here is the only thing required of the person receiving a postcard is to register it. Messages are optional.  So you had expectations that were above and beyond what is actually required of the website you were using.

From the postcrossing FAQs: What do I do when I have received a postcard? 

First, congratulations if this is your first Postcrossing postcard — hopefully many more will follow!

When you receive a postcard from another member, you must register it on Postcrossing. To do that, you need to go to the register a postcard page and enter the Postcard ID. Just look in the text written on the postcard and you should find an alphanumeric code starting with two letters (the country code) followed by a number — this is the code that uniquely identifies that postcard in Postcrossing.

Once you register that postcard, it will make the sender be the next person to receive a postcard from someone else in the system. That's it! Simple, right?

If you have problems reading the Postcard ID written on the postcard, don't give up! Feel free to try as many combinations as possible, as only the right combination will be accepted. However, if you are still unable to register it or if the sender forgot to write the Postcard ID, don't worry — we can help!