i was/were not home?

You should call "If I were not home..." because it is a kind of subjunctive. You may also call it the second conditional.

You should say: -

If I am not home, call me tmr.

This is known as zero conditional.
The format: If + present simple, present simple

We use the zero conditional to talk about events and situations that can occur at any time, and often occur more than once. We can use an imperative in the result clause to give a general instruction.

You can use modal verbs in the main clause, especially can , may

If I am not home, you can call me tmr.

We don’t use first conditional, second conditional or third conditional in the above case.

Second conditional:
You can’t use a subjunctive, If I were not home……… This is not an improbable future situation or event. You are not staying at home all the time. Use subjunctive like the following: ~ If I were you, …If I were the King of England, ….

Use the first conditional to describe possible future events or situations and their result.
The format: If + present simple, will/won’t + infinitive

Third conditional describes a hypothetical situation or event in the past
The format: If + past perfect, would/wouldn’t have + past participle

I,WE,THEY用WERE，HE,SHE,IT,第三身用WAS，明嗎﹖