Why did Ferdinand never track down MK?

Question

"I've always suspected one clone escaped the purge."

_{Ferdinand Chevalier in Orphan Black episode S4E04 "From Instinct to Rational Control"}

Ferdinand admits that he suspected that of the seven clones involved in the Helsinki Incident, one escaped the purge. Even though he didn't seem to have known which one, as evidenced by the conversation that follows.

He even admits as much to (Sarah disguised as) Rachel.

"The Helsinki girls were eradicated in 24 hours. 6 clones, 32 collateral."

_{Ferdinand Chevalier in Orphan Black episode S3E01 "The Weight of This Combination"}

Here he talks about six clones having been eradicated, even though there were seven on the list.

So if he strongly suspected that one of the clones escaped the Helsinki purge, why did he not track her down? He seems to be quite thorough in everything else.

Answer 1

In addition to the fact that Ferdinand didn't know which clone might've gotten away (which you mentioned):

1. He genuinely thought M.K. was dead, at least for a while

   RACHEL: And you're certain Veera Suominen is dead?
   FERDINAND: Yes, Rachel. And Niki Lintula. I... personally confirmed it.

   _{Orphan Black: Helsinki #5 — Kill Switch}

2. Her uncle, and monitor, Matti had a contact help M.K. go into hiding.

   

Episode 4x02 establishes that after resurfacing to Beth, M.K. went into hiding again. The episode also establishes that Neolution (Frank and Roxie) was looking for M.K., though it's unclear who was aware she was alive or how they came to know that.

BETH: You need to drop all this. Go back into hiding. Drink ice tea, play video games, whatever, just stay hidden.
[...]
M.K.: Beth said to hide. Hide your family.

_{- 4x02 Transgressive Border Crossing}

Given that the relationship between M.K. and Ferdinand can really only be described as adversarial it seems the most likely explanations are:

• If Ferdinand suspected a clone escaped, he thought it was either Jade/C35FE1 or Katja. He wasn't looking for M.K. because he really thought she was dead.
• Ferdinand did search for her, but she was too far in hiding and his search was unfruitful.