Where do you live? If the seasons changed dramatically then the guitar would have dried out in the dry seasons, expanded when humid. Temperature changes will also cause expansion and contraction of the wood and this will not be uniform throughout the instrument. This translates to the instrument being a different shape after a year (or less, or more depending on circumstances).
Ideally one should not keep an acoustic out like that. It should be in the case with a damp humidifier in there with it. The humidifier should be checked every day. This is more important in the winter when the air is dry and heat on in the house. In dry climates this should be practiced. It's okay to leave the instrument out if there is some type of humidifier in the house that is on all the time. Some centralized heating and A/C units have humidifiers built in that will blow moist air into the home. Then there are large floor units. Many musicians keep these in their music room and keep the instruments out.
After a year of sitting out and not being looked after I'd guess the neck is warped and needs to be adjusted, as per Tim's comment. However the top could also be warped given that it was not taken care of. If you take it in for an overall adjustment a Luthier will let it sit near a humidifier to reanimate the wood. If it's in really bad shape even an adjustment might not bring it back to its original state.
Typically guitars need an adjustment at least once a year (sometimes every season) even when they are being taken care of properly. I am quite surprised that some people leave guitars out all year and DON'T get buzzing, dead spots, and permanent damage.