i were to come yesterday,but i could not.这个句子算虚拟语气的什么用法、为什么没IF,还有were to不要误解 ,高财富奖励.

这是过去将来型条件从句的缩略句，完整的句子和语境如下：
Why didn't you do....?
Yeah, (if) I were to come yesterday, (I could do...,) but I could not.
If从句 + were to + 动词原形，表示在过去对将来的某种计划和安排，但这种计划最终没有实现。

be to do,将来式的一种
表示根据计划安排做.
不是虚拟,也不是什么条件句省if