Why is there a comma in the Russian sentence? The comma in English would make it seem like a question phrased "I do not remember, where is your box?" Otherwise it just seems like someone out of breath "I do not remember (pause) where your box is."
Would you say "I forgot where your box is" differently? Because it is not accepted. However, in another exercise both versions "They already forgot where her boyfriend lives" and "They do not remember anymore where her boyfriend lives" were accepted.