It looks like the topic title currently has the typo in it:
Looking at the edit history, it seems you accidentally added the d when recategorising the topic:
If you edit the title again to remove the ‘d’, refresh the page, and copy the link, the title in the link should reflect the edit. 
As Moin said, topic titles can change over the course of time so the actual identifier that Discourse uses to find the topic is the topic_id.