Being placed on suspension is not an automatic assumption of guilt and does not amount to disciplinary action. It is there to be used as a precautionary measure whilst an employer investigates any allegations against the employee. Reasons for suspending could be in the case of gross misconduct, breakdown of relationship, risk to an employer's property, their clients or other employees, to preserve evidence or ensure it is not tampered with, avoid potential witnesses being pressured or intimidated, etc.
During the period of suspension the employer should conduct a reasonable investigation into the allegations against the employee. If the investigation gathers enough evidence to justify the taking disciplinary action that could be the next step. In that case the employee has the right to be informed in advance of the allegations against them and be given the opportunity to prepare for the hearing.
On the other hand, if the investigation does not find enough evidence to justify a disciplinary, the employer should terminate the suspension immediately and allow the employee to return to work as normal.
In terms of the message you sent to the other person, the is of course a potential for the employer to find out, for example if they ask that person about it and they provide any information about what you had told them. However, if you had done this in your private time and via private messaging that is not monitored by the employer, then unless the other person says anything to the employer, it is unlikely they will find out about it.
This is your basic legal position. I have more detailed advice for you in terms of what is expected of an employer to ensure that a fair disciplinary procedure is followed, which I wish to discuss so please take a second to leave a positive rating for the service so far (by selecting 3, 4 or 5 stars) and I can continue with that and answer any further questions you may have. Don’t worry, there is no extra cost and leaving a rating will not close the question and we can continue this discussion. Thank you