It does not sound like this is a subpoena, as those are not generally sent through the mail. For you to be arrested for not appearing pursuant to a subpoena, you must be personally served. You should consult an attorney regarding exactly what was served to determine any potential consequences of not appearing.
Being served through the mail has the same legal affect as being served something in person by a process server. Mail delivery is much faster and cheaper than hand-delivery, and is thus used 99% of the time. Hand-delivery is usually used when a person has tried to evade service (by moving, not providing a forwarding address, etc.). The court is summoning you to appear. It would be wise to go.
First of all, any time you get a summons from a Court, you would be a fool to ignore it. It does not require that it be served by hand delivery for it to be valid and effective.
It is difficult to identify exactly what is going on when you do not have all the facts yourself. First I would say that you should contact an attorney so that they can look up the case and tell you exactly what is going on. Having said that, I am going to hazard a wild guess. I think that there is an action in Juvenile Court that is alleging that your daughter was endangered by the situation that occurred. Because you are a parent of the child, you are being served with notice of the case as an interested party. If I am correct, even though I expect that no change of custody would result from this hearing, simply because the Court has the authority to make all kinds of orders affecting custody, you should either be present or have a legal representative present to make certain that your daughter does not end up under the authority of Youth Services (because mom is deemed inappropriate and nobody else stepped up to assure the court she would be safe.
Again, contact an attorney, it will be worth the investment.
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