Disappearing stray cats

I live in Kensington and, over the last week, noticed that a few of the regular stays that normally sleep in my backyard have disappeared... has any one heard anything / noticed the same thing happening?

I wouldn't be worried, as I've noticed the (TNR) boys tend to go for a walkabout every so often, but one female sweetheart who NEVER goes outside of my neighbor and my yards is one of them.....

I have a friend that does TNR in Kensington and feeds a lot of them. Where about are they disappearing? I can ask her if she knows anything.