Retrieving "lost" call on hold

[Van]

Hi,

We are using T42G and T46G in a small office setup.
Some of the users experience in some cases the following behaviour:

Talking with a customer, they put him/her on hold so they can dial another extension but when they hang up the second line the first line seems to be lost.
The first call stays on hold (with MOH) but the phone doesn't show any indication there is a call on hold/waiting.

- Is there a star/feature code to recall a line on hold?
- Is there some setting we can change so calls on hold appear on the phone screen?

Thanks,

Van