When Harmshield lands you should get a message saying "You no longer feel pain."
 

Currently there is no message when Harmshield lands.

Harmshield on Allakhazam.com

Or am I missing something?

According to lucy.allakhazam.com spell data, the original land and fade messages were, "You feel [something]." and "The [something] fades." So probably something like, "You feel shielded from harm." and "The shielding fades." Apparently the "You no longer feel pain." message wasn't added until a newer version of the spell was introduced in 2008:

2008-07-09 02:52
Changed 'Wears off' message from "The placeholder fades." to "Your invulnerability fades."
2008-07-09 02:52
Removed 'Cast on other' message: is covered by a placeholder message.
2008-07-09 02:52
Changed 'Cast on you' message from "You feel a placeholder message." to "You no longer feel pain."

Bard DA is "You feel protected." it's possible that they shared that land message, now to find some evidence.

As far back as March 2002, the messages were:
As of today, the fade message is accurate and the cast message is still missing.