My step dad has been arrested before for GBh and got on probation he then got arrested for criminal damage but no charges was found against him , he got sent to a prison cell because his probation officer is on holiday but what will happen to Him surely he can't get put away for nothing

He got put in a jail ( most likely not a prison) because someone at the probation department put a hold on him at the time of arrest. Most likely unless the details of the crime involved other tech violations he will be released but he can still be held pending a hearing before a judge.