Er ist lange nicht mit mir in Kontakt getreten unter dem Vorwand, beschäftigt zu sein.

I find a trick for remembering “Vorwand” and distinguishing it from other, similar-sounding words, to notice that it contains the word “Wand” and imagine that a “pretense” is just like a wall that a person puts up to shield their true intentions. The word can also be translated “excuse”, which uses a similar logic.