Spray contact adhesive has somewhat lower bonding power than the stuff in cans or tubes, and if it counts I rate the solvent-based stuff higher than the water-based variety. It sounds like you may not have applied sufficient glue to form a good bond (and/or overcome soaking in to the MDF) or the glue itself wasn't strong enough. It may be a silly question, but did you coat both the MDF and the back of the laminate with contact adhesive? You need to coat both mating surfaces. When making commercial shop furniture and counters I tend to use a lot more glue than you would apply from a spray can; the technique is really to get an even coat without any bubbles or "bits" by using a "comb" made from an offcut of laminate (with a very fine saw) and leave both sides to dry for 20 to 30 minutes. Don't leave them apart for too long. When you attach the two pieces start at one edge and sort of roll down the laminate onto the substrate (it needs a 1/2in or so overhang to make this work) and finally add pressure with either a pressure roller or a block of wood with some felt attached (like a blackboard rubber, sort of). As the contact adhesive has already set before lamination it is possible to trim straight away.
As to your problem you may be able to re-attach the surface laminates by removing the edge lipping and gently prying open the imperfect joints between the MDF and the laminate with a spatula or very thin knife, spraying in some more adhesive, rolling the joint shut and clamping together for an hour or so using wooden blocks to protect the laminate. This may work, but often in the commercial environment I work in it's easier and much faster to delaminate the pieces (gentle heat and Evo-Stick thinners or similar), clean off the substrate with the same solvent and once it has all dried to relaminate with a new piece of laminate.