Are there Kabbalistic or Talmudic sources saying that not finding your bashert is a punishment for doing zera levatala (wasteful seminal emission)? I heard a popular rabbi make this claim in a class and it's disturbed me ever since.
The Kabalistic work "Tikunei Zohar" (14) mentions this as a punishment for a person who has relations with women he should not be having relations with. It is stated there that is that this is מִדָּה לָקֳבֵל מִדָּה (Midah k'neged midah).
My understanding is, that by living with these types of women, the person demonstrates that he isn't interested in saving his seed for a kosher woman that is destined for him, so Hashem says, OK, I'll find someone else for her.
It is important to note, that the TZ concludes, that if a person repents, then this punishment is reversible.
Rabbi Nachman of Breslov (Likutei Moharan 2:87) extends the words of the TZ to all forms of defilement of the Bris Milah. However he agrees that this can be rectified; noting, that the month of Elul being especially auspicious for this rectification.