If your boss is unreachable and you have to hand in your notice, then you'd typically go to your boss' boss or to HR. The point is to make sure that someone in the management chain is aware that your notice period has started. Note that this mainly applies to US-standard two-week notice periods as many countries have longer notice periods in which case you can usually afford to wait a few days before resigning.
Alison Green covers the basics of unreachable bosses here:
You tell your boss first. But if your boss is unreachable — out of the country on vacation for more than a couple of more days, for instance, or in the hospital with ebola — then you give your notice to your boss’s boss (or possibly HR if that’s how it’s done in your company). You don’t need to sit around waiting for your boss to come back, if it’s going to be a while — or even if it’s not going to be that long, if it would mean eating in to an already short notice period. (In other words, if you’re giving six weeks notice, it’s fine to wait a couple of days until your manager’s ebola clears up. If you’re leaving two weeks from today, then you need to tell someone that today.)
Source: is it rude to resign over the phone?, Alison Green on April 5, 2013
In another post she also covers how this is a know-your-boss situation. Some will want to their vacation or even sick leave interrupted with news like this so they can start making plans. But I'd wager that the majority won't be that eager to work through a holiday or illness. A notice period is mainly to hand-over your projects and document whatever needs documenting after all. Virtually no one can be replaced in two weeks. Alison goes on to cover the importance of controlling the timing of your resignation and not letting unreachable or uncommunicative bosses get in the way of handing in a resignation.
She's talking mainly about managers who are impossible to get a hold of though. In your case I'd have suggested waiting until Monday if you know your boss to be reasonable. If you had evidence or reason to believe that he's not reasonable and might hold you to an exact 14 days then it would have been best to give notice with HR or his boss immediately. You could then have either waited until Monday to tell him or send an email with HR or his boss in CC.
You already gave your notice via email though and there's nothing wrong with that. It's not ideal but it's a valid way of handing in notice when you have trouble reaching someone. Resigning via email is nowhere near "bridge burning" territory.
In closing, to list methods of letting your manager know you're resigning, from most to least preferred:
- in person
- via phone
- v̶i̶a̶ ̶I̶M̶/̶t̶e̶x̶t: don't do this! this is not a conversation to have via text, call him
- via email
- through his boss
- through HR
As mentioned, you'd typically combine the latter three if your boss is truly unreachable and you absolutely need to hand in your notice today.