Quote:
posted:
non·plussed
adjective /nän'pl?st/
(of a person) Surprised and confused so much that they are unsure how to react
- he would be completely nonplussed and embarrassed at the idea
(of a person) Not disconcerted; unperturbed
Web definitions
at a loss(p): filled with bewilderment; "at a loss to understand those remarks"; "puzzled that she left without saying goodbye"
wordnetweb.princeton.edu/perl/webwn
(nonplus) perplex: be a mystery or bewildering to; "This beats me!"; "Got me--I don't know the answer!"; "a vexing problem"; "This question really stuck me"
wordnetweb.princeton.edu/perl/webwn
Confusion (from Latin confusio, -onis, noun of action from confundere "to pour together", also "to confuse"

of a pathological degree usually refers to loss of orientation (ability to place oneself correctly in the world by time, Citing: Dorland's Medical Dictionary for Health Consumers. ...
en.wikipedia.org/wiki/Nonplussed
(Nonplus) Konstruktivits is a British industrial band. Formed in 1982, they were mostly active in the 1980s, with recording activity continuing until today.
en.wikipedia.org/wiki/Nonplus
Bewildered; unsure how to respond; Unfazed, unaffected, or unimpressed
en.wiktionary.org/wiki/nonplussed
(nonplus) A state of perplexity or bewilderment; to perplex or bewilder someone; to confound or flummox
en.wiktionary.org/wiki/nonplus
does not mean you don't care; non-plussed means you're bewildered.
english-language-skills.com/item/111-deepen-your-vocabulary.
It's a broad word. It was used fine in your example.