The most recent job I worked at things didn't go so well. I always tried my best but for a number of reasons my productivity and relationship with other coworkers were strained. I believe it was a very toxic work environment and I'm prepared to explain why. On my last day I thought I would have until the end of the usual day to talk to my manager about leaving, but suddenly he came over and said he's going to an appointment and needs my badge (so I had to leave right away). When applying for jobs I don't want to have a blank in my work history but if I can't get a reference how can I prove I worked here?
The company I worked for was IBM. One of my managers said "it is company policy not to give references and we can only say yes or no that you worked here". The person who told me this couldn't be trusted to give accurate information, and even if this was true people may not follow the policy anyways.
I'm afraid they will bad mouth me and I won't have a chance to defend myself. What should I do to prevent my past employers from discouraging new employers from hiring me? Should I mention to potential employers that there were issues?