The situation is similar.
Similar to what?
I have a conversation with my friend and request I asked my friend to help me buy a ticket. He/Se didn't just help me - he/she bought it for me!
If your friend had simply helped you buy a ticket, you would perhaps have gone to the train station (if it was a train ticket) together and he/she might have talked to the person at the ticket desk to explain what you needed. You might still have paid for the ticket yourself. If that's the case, then the sentence you wrote isn't correct.
Is the following sentence correct and natural?
My friend bought a ticket for me.
That sentence is grammatically correct and works if your friend used their own money to buy the ticket, or they took your money and bought a ticket to give to you.
We can't tell you if it's natural and appropriate for the context without knowing the context. What sort of ticket was it? Did you go together to buy it? Who paid for it? Why did you need help?
