You did not mention what kind of Gator? White or Natural?
White Gator is inappropriate for spray mounting unless the surface is well sanded (and then wiped very clean with alcohol) to allow for the glue to penetrate. White Gator has a sizing/primer on it that is ready for screen printing or paint, but not glue. Even YES paste will crawl when applied.
Natural Gator is meant to be used with adhesives such as YES or Vacuumount.
The appliaction of the Vacuumount is also important. Did you treat the item being mounted as a Resin Coated Photograph? Did you spray well and give it a 6 minute open time? Did you scrape the surface with a Gator Scraper and then use a d-roller to remove surface dust? Did you wipe the surface down with alcohol prior to mounting?
I sounds like you had two very slick surfaces that would not allow the solvent to fully evaporate and you did not give it enough open time and then it self-dissolved. Or, you did not apply enough adhesive. Or, you did not adequately shake the adhesive and get enough solids in the spray mixture. Or, your surface was dusty and the glue could not penetrate the surface.