I sought to do a query using Excel and MSN Money for CHL and 
it didn't return the company quote I was looking for 
(China Mobile) but another one. 

After reading this message on Microsoft technet:

msn money stock quotes : mystery

I found out that I could also search by ISIN. 

China Mobile (NYSE:CHL) ISIN of US16941M1099

(found ISIN on AdvFn.com) 

It looks like the query "CHL" now does return China Mobile. 

Looking at the results more closely I found that 
there was another query which also didn't return the 
one that I was looking for:

Embraer SA (NYSE:ERJ) ISIN of US29082A1079

So as of this posting ERJ returns Enerji Ltd. (ASX:ERJ)

One thought might be to somehow change the error message for an invalid 
query to indicate to people that they can also search by ISIN. 

I had not heard of the ISIN before looking into this more.

Other tickers could be listed in this thread that 
did not return the company that the person was looking for 

(where the idea would be that generally that would be 
the company that most people are looking for). 

The ISIN could be listed as well, and people could know that 
they can use the ISIN. 

Query of UBS returns Urbas Grupo Financiero SA (BME:UBS).

UBS Group AG (USA) (NYSE:UBS)  ISIN of CH0244767585

For OTC Markets there is no ISIN.

I suspect that effort is made to try to make the ticker
unique across exchanges; but there is no way
way to guarantee this.

For example, there is a company called SHINER INTERNATIONAL
INC which is traded on the exchange OTC Markets with
ticker BEST and then also a company called BEST UNION COMPANY
traded on the Italian stock exchange Borsa Italiana
with the same ticker of BEST (ISIN:IT0004273915).

Google finance uses OTCMKTS:BEST for the former, and
BIT:BEST for the latter.

For the query "BEST" MSN Money returns information about
SHINER INTERNATIONAL.

BEST was also used for a company traded on the
London Stock Exchange called BEST OF THE BEST PLC --
as of April 2, 2015 the ticker has now been changed to BOTB.