When DHS effectuates a removal, a court case is opened up immediately thereafter. Additionally, shortly thereafter, they will file pleadings with the court alleging abuse, abandonment or neglect on the part of the parent. Here, my guess is that DHS will allege that you neglected the child in permitting her to leave the home without supervision.
It is at this point that you would formulate a plan on having the child returned. If the only allegation is that your 4 year old daughter got out of the house on a single occasion, I would suggest that this is not enough to effectuate a proper removal of a child from a parent.
You would need to argue to the judge that this was a simple mistake, it was not indicative of what normally occurs in your home and that the child is not in danger. Based on the facts as you have stated them thus far, I would suggest that you have an excellent chance of prevailing and having the child returned in the very near future.
Please let me know if anything requires clarification.
Also, several customers have asked how they may direct a question to me in particular. If you specifically want me to assist you in your legal matter, just put "FOR JOSEPH" in the subject line and I will gladly pick up the question as soon as I am on-line.