You might want to go back to your agent, the listing, and your title company. Was it disclosed to you that the property was landlocked? Your title policy may show if there is an easement. The title company may also be able to see if the easement is on one of the surrounding properties and just doesn't show on yours.
I wonder...how did you get to the property to view it? Why on earth did you buy first and then look for the easement after?
Good luck. Hopefully, you have cooperative neighbors. If not, you may end up having to get an attorney to see if you can get a "easement of necessity".