There should be an open event for the mobile actionsheet (according to the docs at: https://docs.telerik.com/kendo-ui/api/javascript/mobile/ui/actionsheet/events/open ) but looks like it never fires.
The code needs one additional line to trigger the event:
kendo.mobile.ui.ActionSheet.prototype.open = function(target, context) {
var that = this;
that.target = $(target);
that.context = context;
that.shim.show(target);
that.trigger('open', { target: target, context: context }); /* trigger open event*/
};