Unfortunately this is normal behavior, and a good reason NOT to use master text frames unless absolutley necessary, and if you do use them, never to make adjustmets to size or position on the document page after they have text in them.
When you reassign a master page, for example by swapping sides on a facing pages master as you did, all of the overriden content (anything that you place text or an image into that was originally on the master page) is preserved, and new instances of the master frame are created behind. Any edits you make on the document page, such as moving a frame, unlink that attibute from the master frame, as well, so changes on the master frame will not be reflected on the document page.
BUMMBER! Well thank you for that update! Any suggestions on how we can set this up so that we have editable text boxes that will migrate as we rearrange the pages?
Well, there's the Autoflow Pro plugin from In-Tools.com that might help (http://in-tools.com/products/autoflow-pro/), or turning on Layout Adjustment might help (though probably not). If your frames are snapped to margin guides, they'll probably continue to stay snapped in any case if the page switches sides, but I try to avoid adding odd numbers of pages in the middle of a layout.