How to?: If string contains uppercase ''X'' print("X spotted!")

I'm working on a school assignment and it works (so far) but I don't understand why I had to put the second if statement after else in the tester function for that if p condition (Xavier) to work.

1. I need someone to explain why I couldn't use the if before else in this case.

2. The same condition. It actually needs to test if the user input contains an uppercase X. I have searched online but just can't figure out which method to use.

    def tester(p, givenstring = "Too short"):    
        result=len(p)
        if result>=10:
            print(p)
        else:
            print(givenstring)
        if p == "Is Xavier here?":  # if p == "X" doesn't work.
            print("X is spotted!")
   
    def main():
        while True:
            prompt=input("Write something (quit ends): ")
            if prompt=="quit":
                break
            else:
                tester(prompt)
   
    if __name__ == "__main__":
       main()