Thanks in advance for your time.
I've been unable to attend my classes in the last few weeks for various reasons I would like to keep private. However many assignments I have been able to complete, I have been very late in submitting this one for my first year philosophy course worth 20%. Today is day 11 and I just learned that the assignment was handed back this morning. I'm not asking for compassion. Just complete honesty. I heard that if the assignment is handed back you can no longer hand it in. Is this true? How f*cked am I? Thanks alot.

There's still a chance. Go talk to the professor in person. Email works, but don't expect much compassion. If you're really genuine about your attempt, then go talk to them.

Some professors are heartless, but most (even cruel) will give you leeway.

I Would Go Directly To The Humanities Department. Provide Documentation For The Personal Issue And They Might Accept The Late Submission.

Not to seem insensitive to your "personal issue" or anything,
but assuming you're also in Dr. Allan's class, you don't even need to attend the lectures or even the tutorials to be able to know what's going on. Everything you need to know is in the course pack - the textbook you were told to buy at the beginning of the semester..
The questions were actually really straight forward and easy.. I wrote both of my first essays at around 4am the night before, and managed to get a 76% on the first and 83% on the second..

If you're gonna go talk to Dr. Allan, I suggest you come up with a different excuse than just not being able to attend lectures.

Good luck.

In general, if you miss an assignment or test then you need to submit documentation within five business days. If it has been eleven days, then unless you have a really good reason as to why you could not submit documentation, you're probably out of luck, even if the assignment hadn't been handed back already.

In the case of extenuating circumstances, your Associate Dean's office is your best bet. I recommend approaching them directly. While your professor is the one who will decide in the end, many may simply refer you to the Associate Dean and all documentation will have to go through them anyway. The AD's office is great with complicated situations and is genuinely there to help students and facilitate their academic success. Sometimes things happen, but now the responsibility is on your shoulders to seek out those resources and get the assistance you need. It is there, but you need to access it first.