Thanks for the recommendations.
Whappo: i took a look at Isobuster, it is only for PC and this is a Mac.
Silkoone: Its unclear if it was closed out-i understand what you mean but was using Track burning (TAO) and not DAO which automatically closed/ends the disc.
However, here is something i've since thought about: The MS OS system that was burning the disc was set to TAO and so when i arrived home, i added one more session which filled up the disc but while the CD is full, i don't know that it was closed/ended. I wonder if adding that additional session did something to the earlier burns.
I use Roxio Toast v7 with this Mac and set it for TAO.
When i read "disc info" via the Toast software, it shows the other sessions on the disc, so i know they are there - i just can't get access to them.
I have, since posting this question, tried three different recovery programs and none of them recover anything other then the session i added.
As i erased all the photos on the HD from where the CD was burned i can't return to the originals.
However, it does, again, make me question my system of backing up photos; in this instance i was just traveling from my family's home to mine and didn't think to make two copies even though i had a 4GB flash drive with me that i could have put them into.
Sigh, i think i've reached the end of this trail but am open to more suggestion.
Silkoone, is there a way to close the CD at this point? Toast does indicate it is full and nothing more may be added?