While doing component testing Variant Preview floating bar is disappearing after page load in Experience Editor. We are using sitecore 8.2 (rev. 170728). Please let us know if anyone faced this issue and resolved.
As confirmed by Sitecore support, this issue seems to be known an issue and has been fixed in Sitecore 9.0 Initial Release, see the Release Notes, search for 110468. For Sitecore 8.2 update 5, they provided a patch to fix this issue and the patch can be found in the below URL.