It is common at this age for kids to be so engaged in their play, they deliberately hold it until something more boring comes along. Then, they forget they need to go until it is too late. (I taught preschool, and had the class of kids that were having accidents or were "in training" (they called me the potty wizard I mostly had 2's and 3's but had an occasional four year old that had "reverted" as well).
Since they don't fully grasp cause and effect at this age, it can be a stretch to get them to remember or explain why they waited or why they didn't go in the first place. This would explain your daughter's inability to answer you when you ask.
I wrote a detailed answer about how to deal with it on this question that offers more detail about how to talk to her about why it is important to go so often in a way that will be meaningful to her.
Whether the reason is Partial holding (she goes potty, but then doesn't let all of it out and as a result needs to go again sooner than she otherwise might need to, or simply that your daughter is enjoying play time and doesn't want to interupt it to go potty, the response is still the same.
Make it routine to have her go use the potty frequently whether she thinks she needs to go or not. Every hour to hour and a half should generally do the trick. I also have my current charge (three year old boy) go potty any time we change rooms or activities. That means in order to move from inside to outside he must attempt going potty and clean up the current activity. He goes before nap (even if wearing a pull-up - it is good to practice), he goes before we go outside AND he goes when we come back inside. It is so much a part of the routine he rarely protests even if he has gone ten minutes prior but now we are about to go on a walk. Again, for more details you can look at my answer to this other closely related question.
If the problem continues, asking your pediatrician about it at her check up just before she turns five, would be a good way to reassure yourself there is not a physical problem, or to confirm what the problem is so you know how to address it and move forward.