English Adjunct, Adverb, Adverbial

A poster of http://www.facebook.com/profile.php?id=100001323695366#!/profile.php? on December 04, 2010 asks:  

I’ve a question that I hope someone would help me with. In the following sentence should we use [ left ] or [ had left ] and why ?
** After I had gone home, I realized that I ……….. my wallet at the supermarket. 

And also if we use WHEN in a sentence like this one where it’s followed by three actions, which one should be present perfect and which should be past simple?

In the grammar of English, however, the time is conceptualized as being located on a time axis, and a fixed point on the time axis is the speech time of interaction between a speaker and a hearer when an event occurs in posterior or anterior to it. The event frame locates the event by comparing the position of the frame with respect to the tense locus. The two most important considerations in tense systems are the selection of the tense locus and the nature of the relationship between the tense locus and the event frame. So what we have here is a preterite and present reading. And since English does not have the form for an anterior to a past event, other than the pluperfect (a perfective form), it is the alternative (though the actual reading is ambiguously non-pefective). So it is fine that the temporal adverb be a past reading (‘after i went home’)= “After i went home, i realized that i had left my wallet.” Just sounds like this example: Nels rertired before Max joined the faculty. That's all.