Hello, I lost to the Rocket Grunt at the end of Nugget Bridge and now I can't progress.  
The Grunt disappeared and the one behind the house in Cerulean is unreachable.  
The police still block the house and I can't move forward.  
Please reset the event so I can continue the storyline.  
My in-game name is: Colinah

Hello @Colinah. Sorry for the late response.

 

This NPC is intended to disappear after battling him, regardless of the outcome of the battle.

Your next step now should be to challenge the Cerulean City Gym to obtain the Cascade Badge. Once that is obtained, the police officer blocking the way will allow you to pass so you may continue onto Vermilion City for the third badge.

Make sure to grab the SS Anne ticket from Bill in Route 25 before leaving Cerulean City as this item is needed to progress the story in Vermilion City.

 

If you have any further questions, please let me know.