He wasn't asking about the possibility of charging the person
successfully. The issue on evidence is separate issue under
criminal procedure, and the investigator might be able to
obtain a confession with the right interview techniques.
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However, in order to proceed with a criminal case, the concern
is whether the person committed an offence in the first place. If
you look at Penal Code section 415, the incident must satisfy
2 criteria:
(i) Act of deliver property/consent to retain property/act or
omission that causes injury (harm to body, mind, reputation,
property) or won't occur if the victim was not deceived
(ii) Intention of the accused at the time of the act
involved deception to dishonestly (wrongful gain/loss) or
fraudulently induce (i)
If the intention of not returning the money does not coincide
with the time of the act, Cheating is not the appropriate section
to apply. There might be other relevant sections like Criminal
Misappropriation of Property.
The other alternative is to proceed as a civil case rather than
a criminal case. In a civil case, you need to engage your
own lawyer to seek compensation for the tort. In a criminal case,
the prosecution will seek punishment for the offence but you might
not receive any compensation.
You might wish to seek legal advice from proper channel if so
desired.