In some states and certain counties in California, bail forfeiture can be used as both a means to be released from jail and to close a case. Bail forfeitable offenses are typically misdemeanors such as traffic violations.
In California, if you are a co-signer and you wish to revoke a bail bond, you will need to contact the bail bond agency and explain the situation. You will need to liaise with the bail bond company and ensure that the relevant courts are aware of the changes to make the decision official.
The legal implications of bail bond forfeiture can be severe. Beyond the financial loss, the defendant may face additional charges for failing to appear in court, complicating their legal situation.
Generally, a bond forfeiture would just revoke liberty and have the defendant return to jail pending trial. So no, a bond forfeiture is not analogous to "guilt" or conviction. in lieu of conviction is "in place of" or "instead of," so alone, that is not a conviction either.