Precisely. She has shown herself capable when she helped prove Lyney's innocence and solved the serial disappearances case, and since she is already acquainted with Tartaglia she may discern things that others would miss.

[ Out of everyone Neuvillette knows of, he believes her to be the one most likely to figure out the truth behind Childe's sudden disappearance. Briefly, he wonders how their investigation is going; it's only been two days since he brought them to the elevator behind the opera house so realistically they haven't made much process yet, but he is hopeful. At the question, the Iudex brings a gloved hand to his chin in thought as he mulls over such a possibility. ]

...Such a scenario cannot be ruled out. The Fortress is as big as a city, with several abandoned zones and arkhium mine shafts. Even the most thorough search might miss something, whether by mistake or by malicious intent.

[ For example, if Childe was brought to a part of the mine people didn't go to even before mining operations halted and one of the guards on the search team deliberately misled the others to prevent him from being found... he trusts Wriothesley fully, but it's entirely possible that someone working under him might have reason to get rid of the Harbinger. ]