For asynchronous invocations in UML, when an exception is thrown and there is no matching exception handler within the activity, the exception is effectively lost because there is no direct mechanism to propagate it back to the caller. This reflects the nature of asynchronous communication where the calling process does not wait for the completion of the called process and, thus, may not be designed to handle exceptions that occur during the called process.
References:
* UML 2.5 Specification: The UML specification describes the behavior of actions within activities and how exceptions are handled, or not handled, in the case of asynchronous calls. It specifically states that for asynchronous calls, the exception is not propagated back to the caller as there is no return flow defined for such invocations.