I was hired as an employee (Rails developer) with a 3 months trial. However, I was fired at week 2 with the excuse that I was having "problems". Not sure what h

I was hired as an employee (Rails developer) with a 3 months trial. However, I was fired at week 2 with the excuse that I was having "problems". Not sure what he meant since I delivered features and I was working on a task at that time. I was even making progress and communicating with the team. I was also trying to learn about the codebase. They were two apps so I had a lot to learn. I had done scrum and pairing too. The person who fired mentioned problems with their budget and he said something like they wouldn't be able to afford me if I had to take time to learn their codebase/platform and what they've done, and while that sounds reasonable I don't think they should have hired me in their first place. I don't think I'm being unreasonable here? I might have done mistakes too perhaps, but I don't think it's fair the way things ended. I think he also said that he had to fire someone else and that he would like to keep an open door for further work but I don't think I'll join them anymore if they ever approach me again. After being fired at week 2 I don't want to get let down again.