When I’ve been scarce, as I’ve been these past months, this is the first question I am asked. 

It’s quite a complex little word, and as is usual with isiZulu it conveys a complete sentence. 
Here’s how it works. 
u-zi-fihl-e-phi?

you-yourself-hid-past-where?

where have you been hiding yourself?
The first syllable is a low tone, an 8, and means “you”

The second syllable, in the object concord position, is a reflexive concord. It turns the verb back upon the subject.

The next bite is the isiqu, in this case one denoting hiding, concealing, keeping secret.

The penultimate syllable shows the simple past tense, that the verb happened sometime before this.

Finally, there is the locative interrogative suffix, “where?”
That’s the technical aspect of the word. What it actually means is far simpler.

“I’ve missed you.”