Hi, I'm so sorry to hear about your frog! I know it is so hard when we lose a pet and we're not sure why...
Two forum members created this wonderful list of questions that you could answer, it would certainly help all of us try and figure out what happened...
I'm copying and pasting it below:

Trouble in the enclosure or a frog is ? sick ?
It is great that one seeks advice ! After all, that's why we are here !!!
There actually may be nothing wrong , or conversely, a change in behavior warrants keeping a close eye on your froggy friend !

'patience is a virtue' AND 'time is of the essence'

If there is trouble in the frog enclosure it will be very helpful if one could provide as much of the following information as possible:
THEN---- post this information in the proper forum area to get advice from FF members that keep the same frog so there is no confusion

1-size of enclosure
2-# on inhabitants - specifically ( if there is another frog ---size differences ?)
3-humidity
4-temp
5-water - type - for both misting and soaking dish
6-materials used for substrate
7-enclosure set up i.e. plants( live or artificial) wood, bark etc -how were things prepared prior to being put into the viv
8-main food source
9-vitamins and calcium ? ( how often )
10-lighting
11-what is, specifically, being used to maintain the temperature of the enclosure
12-when is the last time he ate
13-have you found poop lately
14-a pic would be great ( including the frog ) any little cell phone pic is fine
15- how old is the frog
16-how long have you owned him
17- is the frog wild caught or captive bred
18- frog food- how often and if its diverse what other feeders are used as treats
19- about how often the frog is handled
20-is the enclosure is kept in a high or low traffic area

If I have left anything out, please feel free to chime in !
Lynn -AND -- Thank You Grif !!!!!!!!