After a long day of driving, we arrived to our assigned room at about 7pm to find a Do Not Disturb sign on the doorknob. Returned to check in counter to inform them; they checked the computer and instead of physically verifying the room to be vacant, indicated that housekeeping must have forgot to remove the sign. Our keys provided access, and upon entering, noticed someone elses personal ptoperty in the room and on the bed, while the occupant may have been in the closed bathroom. We quickly exited and returned to the check in counter to inform them, and that we know longer felt safe or comfortable staying there, as our improper entry could have had very bad results for us and/or the occupants. Additionally, we were justifyably concerned the same thing could potentially happen again to us if we were in another room. We ultimately stayed at an adjacent hotel which was very nice.