I won my battle with Brock and he gave me the TM to hit the large trees, so I went to choose my pokemon but my came closed unexpectedly so when I went back on I could no longer get it! Is there a way to get it back?

Hello @Tismeemily

 

Sorry to hear you're unable to Headbutt after defeating Brock.

 

When defeating Brock, he gives you the Boulder Badge, which allows you to use Headbutt on trees if your Pokemon has at least 150 happiness. However, Brock doesn't give you the Headbutt TM itself.  

 

To get Headbutt, you can go to the Headbutt Tutor in the Viridian Forest Maze.

 

When you first enter the maze, its extremely dark. Move north past the first left path to take the 2nd left path, and follow that do west and south, bringing you to the Headbutt Tutor,  who will teach the move to your Pokemon for $2000. If there is someone in the way, talk to NPC Jerry outside, who needs help getting their Pidgey back. In front of the Tutor will be a thief, whom after you fight, will move and allow access to the Tutor (Jerry will also reward you for the help).

 

You can also purchase the Headbutt TM later in game at the Department Stores. 

 

Let me know if you need any further help getting Headbutt.