Should contractor give you a warranty?

My mother hired a guy who installed a 2 ton AC unit to her house. The guy was referred by her friend Larry. My mom say she trust the man but never saw that guy a day in her life. She trust the guy simply because he was referred to her by that guy Larry. The man did the job in about 4 hours just by himself. I never knew you could install a unit that quick. My mom is disabled and over 65. I talk to her and she curse me out telling me it's her money but I do not want her to get screwed. I want her to have her warranty but he claims that he will give her a copy. It's been over four days and no warranty. Should I be concerned. In all honesty the warranty may not even cover any cost if the unit breaks down because he was not contracted and did a quick job installing it. I am stressed because she spent a lot of money on that unit.

Should contractor give you a warranty?
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