Should I trust a study that doesn't mention sample size, but that is published in a scholarly journal? I'm doing a bit of research on the exchange experiences of international students for my supervisor. 

I came across an article in the Journal of Education for Business that is relevant to my topic: 'Confronting Diversity Issues in the Classroom with Strategies to Improve Satisfaction and Retention of International Students.' The authors conducted surveys of Business faculty and international students, and they ran some focus groups. Here's the thing, there's no indication of the sample size in the methods or results (or anywhere so I don't know whether they surveyed 10 professors or 100. The survey results are all given as percentages so there's no way to infer the scope of the study.

I am skeptical, but they were also published in a scholarly journal, so they must have passed peer review right? The information is good so if I could, I'd like to use it.
Why don't you write the corresponding author and ask them what the sample size was. You can always cite the sample size, if you decide to use the study, as a personal communication.