You appear to be having a problem understaning the prior posts. Notsosure1 was think about what is and is not a socially acceptable way of offering help.
So not about what the employee may or may not have actually done or said to the girl. It was about what Notsosure1 deems to be* socially acceptable. The next (?) post had a "rape fantasy" and used a third party personal pronoun for the girls body part so I suspect that what is socially acceptable for Notsosure1 *would not be the standard applied by most people.
Summary for below : M&S has a safeguarding issue which needs to be fixed.
If any of the three specific actions which Notsosure1 was thinking about had happened ( that employee or indeed any employee (male or female) had asked about the girls breasts etc. rather than a generic enquiry ) then M&S would have had mother complaining about what is very very clear safeguarding problem.
Such specific employee conduct would have moved the complaint from a potential non-contact child sex abuse incident involving a member of their staff to a possible non-contact child sex abuse incident.
At that stage the manager in charge of the branch and more senior staff would have had an obligation to carefully consider the next steps. Non-contact child abuse is a criminal offence and would fall within gross misconduct grounds for sacking the employee.
I think in the 3 situation outlined by Notsosure1 it would be fair for management to make a judgement call and
• to make a police report and supply the police with any evidence which M&S has in its posession
• for M&S to put the employee on paid leave.
However "paid leave" in real terms could be no pay if the employee was on a zero hour contract and as the employee would still be employed any social welfare claim could be unsucessful. Finding a new job could also be complex as the employee would be under investigation for what could be a serious criminal offence. (And security staff move between local retail companies so gossip could follow the employee locally).
And police involvement is an issue too.
Sacking over a serious alligation when the employee has 'obtained' a not guilty verdict in a criminal court are deemed unfair dismissal and the employee would have suffered economic hardship as a direct result of M&Ss decisions.
Summary M&S has a safeguarding issue which needs to be fixed.