Can I switch "the" to "a" in this context? 

> 
> **Tom:** Can you play ***the*** video?  
> 
> **Ann:** Video? What video? (the person doesn't remember)  
> 
> **Tom:** We watched ***a*** video 10 minutes ago.
> 
> 
> 

Is the last sentence okay?
As for a learner who doesn't have the articles in her mother tongue, I want to be sure.

Another question: [go to a concert vs go to the concert](https://ell.stackexchange.com/questions/140453/go-to-a-concert-vs-go-to-the-concert)