The project manager has taken a risk mitigation approach by buying the item from another vendor who can supply it immediately. Risk mitigation is a strategy that involves reducing the probability and/or impact of a negative risk to an acceptable level. By purchasing the item from another vendor, the project manager has reduced the impact of the delay on the project schedule, even though it may have increased the project cost.
Risk mitigation is different from risk transfer, which involves shifting the responsibility or burden of a risk to a third party, usually through a contract or insurance. Risk acceptance is a strategy that involves acknowledging the risk and being prepared to deal with its consequences. Risk sharing is a strategy that involves allocating some or all of the ownership of a risk to another party who is willing to take on that risk, usually for some form of incentive or reward. References = CompTIA Project+ Study Guide: Exam PK0-005,
3rd Edition, Chapter 7: Risk Management1; CompTIA Project+ Certification Study Guide, 3rd Edition, Chapter 7: Risk Management2