The log.trc file is missing The log.trc file is missing on the server, but there are archived trace files like (log_15.trc, log_16.trc, log_17.trc, log_18.trc, and log_19.trc).  Is this something to be concerned about?  

Is there a way to create the log.trc file?
This is nothing to be concerned about. The default trace creates up to 5 rollover files, each with a max size to 20MB, and a incremental number is automatically appended to the file name. The older files are automatically deleted once the max of 5 files is reached.

You can query the trace in T-SQL using fn_trace_gettable, specifying only the base file name log.trc along with the number of files to read or default to read all available trace files.