Constant Content

I've recently been added to My Projects. I looked at what was available and began to write an article but didn't claim it.
Today, when reviewing My Projects, I no longer saw this request, and others were missing too. Does this mean other authors claimed them? I wasn't sure if once you claimed an article you had exclusive rights to it. If this is the case, I'll be sure to claim the request immediately before beginning the article. I suppose all is not lost. I can change the title and add it to my catalogue.

Thanks in advance for your help.