Did you copy and paste the image OR did you just link to the image.
If you copied the image, it should stay as it was stored as a picture in the blockchain.
IF you just linked to it, then you will get whatever image is posted on that server as that picture. There are actually options on servers to block people from streaming an image to another page - maybe this has now been turned on because you were using their server resources - which is a big no no as it's tantamount to stealing the bandwidth that they have paid for.
The only other explanation I can think of is that it is some feature of SteemIt, but I think this is highly unlikely.
I have the downloaded images/gifs on my computer and so I click and drag each into the posts. I think it might have been an internal issue with the server.
I'm very glad that it was able to fix itself. Little Helper's daily posts have resumed!! :D