1. 查租约,一般如果用了标准租约,会有24小时 notice clause let you in the property.
2. 没有租约,consult a lawyer. Doesn't have to hire him but use the free consultation to find out if you have good chance. And you can pay minimun to have him write a simple letter to state your rights and consequencese.
3. Who is your buyer agent? The buyers agent should represent your interest in this case. If you used listing agent as due agent, he/she still is legally bound to represent your interest otherwise he/she conducted the business illegally.