Question: why this unwrap throws?

extern crate config;

use std::collections::HashMap;

fn main() {

	let mut settings = config::Config::default();
	let file = config::File::with_name("bla");
	{
		let result = settings.merge(file);

		match result {
			Ok(_) => (),
			Err(e) => {
					println!("{:?}",e);
					println!("Failed to read the settings file, skipping...");
			}
		}
	}
	settings.merge(config::Environment::with_prefix("bla")).unwrap();
	println!("{:?}", settings.try_into::<HashMap<String, String>>().unwrap());
}

The Environment::with_prefix unwrap panics. Why does it? Output:

configuration file "bla" not found
Failed to read the settings file, skipping...
thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: configuration file "bla" not found', src\libcore\result.rs:906:4
note: Run with `RUST_BACKTRACE=1` for a backtrace.
error: process didn't exit successfully: `target\debug\vault-unseal.exe` (exit code: 101)

Start by tracing the settings.merge(config::Environment::with_prefix("bla")) call and compare it with the earlier matched merge result. Reproduce the missing-configuration case and determine what error handling the issue should document or change; completion requires a clear explanation of why the unwrap receives an error.