Hi Karly,
This is by design.
When you choose an image we do not load the image onto the server immediately so when there is a reload for security the browser clears the selection.
Otherwise you might be able to spoof the upload process and create an exploit.
There is a way around that and that is to use AJAX to immediately upload and validate the image and save it to the server. That way the link can remain.
However, that takes a rebuild on the image upload and not a supported feature so I do not have any coding to provide on that to help out.
If you think that is something you would like as a feature I encourage you to visit our User Voice Page and either upvote an existing request or make a new request there.
http://tribe.uservoice.com/
Let me know if you have any follow up questions.
Thanks