Selecting or ignoring filtered/hidden cells

While working with CSV log files yesterday, I filtered rows and hid columns to be able to see the data I was interested in. I could select a range of cells and copy, and when I would paste, only the visible cells would paste. (This was obvious from the dotted selection outline drawn around the hidden cells.) Alternatively, I could delete a range of cells, and only the visible cells would be deleted. When I removed the filter, the contents of the previously hidden cells were still there.

In the middle of working with these files, this behavior changed. When I tried to copy a filtered range, all the hidden cells copied too. When I tried to delete a filtered range, the non-visible cells were deleted too.

I am not aware that I did anything to change this behavior. Is there some way to toggle this feature that I could have accidentally changed?

I got back to working on these files again today, and the behavior was back to as originally described.

Has anybody else experienced this? Is this a bug in the program or an intentional feature?