How do I get my 2 month old to suck her thumb rather than a pacifier? ?

For the last week or so my daughter keeps waking after 40 minutes of sleep during the day and I can not resettle her. Usually I just pop the pacifier back in and she goes back to sleep. Now she won't and nothing will settle her except sleeping in my arms. She still wants the pacifier as she cries if I try to get her to sleep without it. She has just started sucking her fingers and fist but can't coordinate them well enough to be completely soothed. I would prefer her to suck her hand than a dummy as then it is always available to her.